I enjoy how many pieces you can scan over when browsing through the site, but I feel by limiting to just small thumbnails and so many to one page, a lot of great art can be missed, or people can get frustrated because the preview looks great but loading the full size image turns out to be a complete let down. Furaffinity (i'm sorry to use that site as a comparison) used to have the same thumbnail system, but once they trashed the thumbnail approach it was so much easier to filter through work on display and I think overall, the community was positive about the change.

An alternative could be if thumbnails are an option, space them out a little more on the browsing screen, maybe make them bigger to see details more?

OR scrap uploading your own thumbnail and use that nifty-awesome thumbnail generator that has been implemented so well into Weasyl, but make it a set dimension and anything above so more of the image is forced to be shown rather than people choosing to display just an eyeball or certain unmentionables.

I don't understand the logistics of coding and how much space it takes to do one layout over another so of course my suggestion could be taken with a grain of salt

TL;DR: Scrap thumbnails for better viewing of submissions, or find alternative.