For future proofing, let's include the following parts that I'm sure are familiar to all included, they're ze rules after all. Please note I'm not officially qualified judge and might have missed some simple thing somewhere but rules as written go as follows.
www.vekn.net/tournament-rules/4-tournament-game-rules
4.1. Cards Allowed
All cards in a player's deck must be genuine Vampire: The Eternal Struggle or Jyhad cards or official V:EKN issued cards from the only authoritative source www.vekn.net as listed here:
Danse Macabre
The Unaligned
Storyline Rewards 2015
Anarchs Unbound
When using V:EKN issued cards they must be preferably color printed on standard paper and inserted into opaque sleeves before another Vampire: The Eternal Struggle or Jyhad card, this requires opaque sleeves for the whole crypt and/or library. These cards are not considered as proxies. See http://www.vekn.net/official-expansion-sets
If cards with distinct backs are used in the same deck (e.g., Jyhad and Vampire: The Eternal Struggle cards, or upside-down 3rd Edition cards and right-side up cards, or mis-cut cards, or cards without the Deckmaster logo) are used, in order to prevent a significant advantage, all cards from the different sets, printings, etc. must be of sufficiently mixed card type, unless they are all sleeved with opaque sleeves (recommended).
Banned List: The following cards are banned in all V:EKN tournaments:
Anthelios, the Red Star (Promo)
Dramatic Upheaval (V:TES)
Edge Explosion (NoR)
Gypsies (V:TES)
Kindred Restructure (V:TES)
Lilith's Blessing (Promo)
Madness of the Bard (Dark Sovereigns)
Memories of Mortality (Ancient Hearts)
Protect Thine Own (Ancient Hearts)
The Return to Innocence (Ancient Hearts)
Rom Gypsy (Dark Sovereigns)
Seeds of Corruption (Ancient Hearts)
Succubus Club (V:TES)
Tarbaby Jack (Black Hand)
Temptation of Greater Power (V:TES)
Terrorists (Ancient Hearts)
Tsigane (Dark Sovereigns)
Any cards that are usable only when playing for ante, including:
Cunctator Motion (V:TES)
High Stakes (V:TES)
Playing for Keeps (Dark Sovereigns)
Note that rules cards from Nights of Reckoning are legal for V:EKN play in both Constructed and Limited formats.
Hmm. If altered art is atop "genuine Vampire: The Eternal Struggle or Jyhad cards or official V:EKN issued cards from the only authoritative source
www.vekn.net as listed here:" and "
If cards with distinct backs are used in the same deck (e.g., Jyhad and Vampire: The Eternal Struggle cards, or upside-down 3rd Edition cards and right-side up cards, or mis-cut cards, or cards without the Deckmaster logo) are used, in order to prevent a significant advantage, all cards from the different sets, printings, etc. must be of sufficiently mixed card type, unless they are all sleeved with opaque sleeves (recommended)." are fulfilled conditions, altered art does not interfere with tournament rule 4.1 as it is currently written.
4.2. Card Interpretation
The head judge is the final authority regarding card interpretations. All cards are to be interpreted according to their most recent printing. If the head judge determines that a player is using older cards and/or misprints to create an advantage by using misleading text or artwork, that player will be subject to the appropriate provisions of the V:EKN Penalty Guidelines.
4.2 seems to be the football referee type of deal. Aka if the altered art is determined by head judge to fulfill "... that a player is using older cards and/or misprints to create an advantage by using misleading text or artwork, that player will be subject to the appropriate provisions of the V:EKN Penalty Guidelines."
So unless the head judge sees no problem, there is no problem with 4.2 by altered art cards.
4.5. Proxy Cards
As long as the game is not under production, the organizer of an event that is neither a National Championship nor a Continental Championship can choose to allow proxy cards in his or her event. For events where proxy cards are allowed, several points apply:
there are no limit to the number of proxy cards a deck can have
every proxy card must be a color-copy of the original card, on standard paper
the quality of the print must allow the reading of the illustrator's name
the organizer must mark the event as 'allowing proxy cards' on the VEKN calendar"
Proxy-cards must be inserted in an opaque sleeve (along the rest of the crypt and/or library), before a regular VTES card.
Otherwise, the use of proxy cards is not permitted, unless a judge provides these cards. If a card becomes excessively worn through play or accidentally damaged in the current sanctioned tournament, or if the owner of the card must leave prior to the conclusion of a game, the judge may provide a proxy replacement card or (in the case of damaged or worn cards) require the player to sleeve all of his or her cards before play continues.
When a judge creates a proxy for a player, it is included in the player's deck. The original card is kept close at hand during the game, if possible. When the proxy is in play, replace it with the original. When it returns to the player's deck/hand, swap it with the proxy. This replacement method helps ensure that the opponent is able to clearly see the intended card and to avoid confusion.
The term "proxy" includes counterfeit cards or any card that is not a genuine game card. Counterfeiters will be prosecuted to the fullest extent of the law.
Proxies are their own thing, it seems with the current rules "every proxy card must be a color-copy of the original card, on standard paper" seems to indicate you cannot proxy altered art cards unless of course it's a judge who produces those cards. Please note the Counterfeiters will be prosecuted to the fullest extent of the law part. Proxies are very serious business.
And... well, yeah. Unless the altered art is on the backside or sides and can be assumed to be part of a marked card attempt to gain advantage, it seems rules as written, say genuine vtes or jyhad cards can have as much signature or whatever atop it as long as head judge is okay with it.
Naturally this means it can wary from judge to judge but that's tournament rules for you. Cannot account for everything and there's need to leave wiggle-room as otherwise fullest extent of the law will be brought upon those who dare to play Hugh signed cards in tournaments instead just having them collect dust. After all why is signature somehow less altered then putting googly eyes herp-derp stickers on Sheldon then sleeving it. I base this somewhat on the explanation provided what constitutes a proxy
www.vekn.net/tournament-rules/appendix-b-definition-of-terms
Proxy Card: A card used during competition to represent another card; also counterfeit cards, or any card that is not genuinely produced by the game's manufacturer.
If it's not googly eyed Sheldon trying to be Arika, or printed/third world knockoff Sheldon cardboard, then it is not proxy. Genuine cards do not become proxies if they represent what they are. Head judge is the ultimate referee until the rules as written are changed.
Altered art legality
Potence, if it doesn't work, you just aren't using enough 
Ratings Coordinator, Rules Director
