Some suggestions for Threadless specific to the critique/submission process:

1. The GIF / Critique process. Please allow the 180x100 GIF to be changed when moving a critique to a submission, as the first version (and its GIF) are (for me) early in the design process and while the finished large jpg is updated with the versions, the final GIF is not and might hurt overall presentation.
2. The description of a submission... There a few issues I have with this, the first is that, once written, its not shown a second time on the preview page which asks if this "looks right" or you should "try again". It should be there so you can check over what youve written. To further add to the problem, sometimes the HTML doesn't come out right-- so you might have double and triple checked grammar and spelling, only to find the description still comes out wrong once the submission actually goes through. I would suggest both putting the description on the preview page, and allowing people to edit it after submission (to allow people to reply to common misinterpretations or fix errors they later find in the description)
3. Page memory. When you get to the preview page ("this looks right", "try again" page), if you hit try again, it sends you back to the previous page and erases your selected upload file and description... couldnt this be made so that it retains the data youve entered as this can be kind of annoying... especially if you didnt save the description.
4. Submission file size requirements. Could the 250kb limit be upped? I find I have to reduce quality in Photoshop to near around 70/100 in JPG quality to get some of my images to 250. With an extra 50-100kb of allowable space, it could improve quality easily to 80 or 85 in such situations. I know you cant make it unlimited because people would make flash movies, but a little more headroom would help-- and I cant imagine given todays hardware that a 350kb cap would be technically difficult.
5. Embed Banner Variations. More banner embed options/colors for websites. As of now, there are two, both with a white/light background... Perhaps options with dark backgrounds and of different orientations?

Non-Submission Related:
6. Comment Editing... with Edit and Delete options? This one has probably been suggested before and Im sure there are reasons against it... and if thats the case, how about allowing maybe like 1 minute to edit/delete before locking the comment?

All relatively minor suggestions, but I do think they would improve the site. Thanks for reading!