Decide whether your site is primarily about drawing or image sharing. I think working on the drawing will bring a smaller but more stable community over the long term; however you have more chance of making a buck with the sharing. I can't see what you offer for image sharing that Twitpic or something does not, however.

Then, start over with your user interface, maybe with help from another person. It loads quickly and smoothly, so I can see you have put in some work.

But visually...I'm sorry, it's ugly. The colors and fonts seem to have been selected at random and there are too many things competing for my attention. The first thing I notice is that few or none of the users are paying any attention to your 'theme of the day,' so maybe the theme is pointless; you can get rid of multiple UI elements immediately. The center window changes size depending on the task (browse/search/draw) - very disorienting. And adding your website to the corner of the picture you uploaded...well I see why you do it but it's just annoying, and it often covers part of a caption. Make a logo, make it small, put it in the top left corner.

There is potential, but please work on simplicity and consistency first. Right now, it's like a meal with 7 courses jammed onto one plate.