First of all, evilchelu, dira, thanks for spending so much energy on something so awesome and unexpected for our little community here. It really is a great thing. I hope you keep going.
Some ideas/thoughts now:
1) Wrap-around board, always fun to look at when it loops and loops. For this, have a viewing option where the browser goes full screen and the entire viewable area is the completed collab, repeating on all sides, then change the cursor to a "panning hand" (typical open-palm, flat hand, ya know. . .) and allow for click & drag panning. I'd maintain the rollover info when hovering over each tile, if possible. I suppose a "Leave Fullscreen" button floating somewhere would be wise UI.
2) Arglye's idea for commenting on a certain board I must second! Having a thread here for each collab is fine, in the meantime. Instead of typical forum commenting capability, like we have here, how about a chatbox type thing instead?
3) In a collab's page, add a list of artists that have submitted tiles so far. Include how many they're done, total. Maybe an avatar associated with their name, though that'd probably take up too much room. This would be a low-priority chunk of information in your UI, IMO, TTYL, OMG, LOL.
A) Before doing any intensive work on upgrades/add-ons to your tzigla concept, it may be wise to run the idea by the folks here first, or other users, whoever they are. Certain ideas will be strongly favored over others.
It's your baby, but if you were to give us a little more power to influence the development of tzigla I think it would benefit everyone. For instance, expose your to-do list, keep a live copy of it somewhere for us, like a change-log to be, and allow voting to determine the priority of things. This way, the most desired things have a better chance of being added the quickest and therefore the appeal of tzigla rises as fast as possible for the majority of users. It only makes sense. How much of the dev you want to "share" is the question.