Currently, the images appear to be resolution 90x90. That's not bad, however it's a scaled-down version of the original images. The original images can be found at Wikia's Github site, in slightly more glorious 128x128 resolution. It'd be a tad more authentic to upload these original images.
I've downloaded the entire Wikia repository (200 MB ZIP file) to my computer, and located the original images. D'you think that I should upload the 128x128 versions over the 90x90 versions?
When you upload an image to serve as a badge via Special:AchievementsCustomize, the image is stored as a File: on the wiki in question. It will have a defined filename: for example, uploading an image to replace the Art Lover badge, my example image, would be stored at File:Badge-picture-4.png.
As it is, files on this wiki are stored at imagined, yet logical locations. My example image is stored on this wiki at File:Art_Lover-icon.png. Since the location of the file is relevant to any attempts readers may make to customize their badges, I think that it would be a good idea to move the files stored on this wiki to their locations as they would be if uploaded through AchievementsCustomize.
As a side note: once moved to these locations, I think the images will be referenced by the Achievements Wikifeature: they will become those that appear when a user gets a badge. Since they should be exactly the same as the default badges, this should have no real effect on anything.
What do you think?