I know that there is a possibility of someone right-clicking and using my art without paying for it(even if it's at a terrible resolution) but I don't want to put gross watermarks over everything that won't do much to deter a determined art thief. How else can I protect my art?

maybe have it on a background?

Lower resolution previews, gradient backgrounds that are more difficult to cut away with a colour picking tool, and slightly rotating/tilting the assets seems to be the norm when looking at existing art assets on the site!