Seperating beginners from the rest.

[Ultimecia]

Not to mention it would be "elitist" to make the expert forum hidden. Some newbies are already bashed (granted, some need them), but creating an invisible expert board isn't going to create a "clubhouse" or something?
I think if you want to create one expert board, then make it read-only for non-expert spriters, or only expert spriters can create new topics.
Or even create one Intermediate session, so it would be like this:

Beginner - Basic recolors/changes. Learning level. Everyone can create topics (post sprites) and comment
Intermediate - A bit more complex edit and some brand new creations. Intermediate users can create topics (maybe Experts too?) and everyone can reply
Expert - Over-the-mill sprites and sheets. Only experts can create topic, experts and intermediates can reply and beginners can read.

To decide which users are beginners, intermediates or experts, maybe there should be two ways: one is having the Sprite Discussion mods and the admins to promote. Another is to have a topic to have popular votes. The ones with more votes in a month or a pretty good amount of votes from different users in a handful months are going to be promoted.