Based on my expierence on FreeNode's LaTeX IRC channel over the last years, I don't think an extra channel dedicated to TikZ questions only would solve the problem of "lazy" new users. Additionally to what has already been mentioned in the comments, my concerns are the following:
- The chat room is hard to find. It took me several months on this platform before I even noticed that TeX.SX has its own chat room. At the time I joined it, there were about 20 users in it and it didn't seem pretty active.
- Especially new users tend to be really impatient when waiting for an answer. This isn't probably so much a problem on the main site, as opening new threads/questions doesn't indicate real-time responses. But in a chat room people want their answers now. I've seen this so many times that people aren't able to wait at least 10 minutes for someone to respond to their questions. Of course, not all people are like that, but the impatience threshold in a chat room is certainly lower. So would there even be enough people around in a TikZ-only channel that are able to respond fast enough?
- On the other hand, users that are already more familiar with how the platform works know they cannot just post "Please, how to draw this picture???" questions without just getting a comment asking about what they have already tried. These people probably would only use the chat if they have an easy or quick to solve problem for which it would take too much time to prepare a full example document. However, if the channel isn't very active and an answer would take as much time as waiting for an answer on the main site, they probably still wouldn't use the chat much.
What would be more helpful, in my opinion, is an FAQ-like thread with links and small examples to the most common graphics problems people are trying to solve. Something similar to TeXample but more concentrated and perhaps also with non-TikZ-based options. You need a simple function plot? Here's a small code snippet how to draw one using
pgfplots. Change this line to plot another function. Follow this link if you want to customize the axes. You need to print a hierarchical tree structure? Here are your options. etc. etc.
If we had such a really concentrated overview which provides starting points to further examples and references, it could be used in the standard response comment, just like MWE or MWEB usually are. I don't think this will reduce the number of those do-it-for-me questions, but I presume it would be more helpful to the users asking such questions than an extra chat room.