Turns out when uploading new files to Sega Retro you’re also responsible for making the link to them from the page to which they’re relevant, so I had to learn some MediaWiki cut’n’paste to make that happen. = p
And I only boned up ONE thing in the process, that I know of (ie uploading a thumbnail manually and then belatedly finding that no you use the one that’s already auto-generated and now you’ve uploaded a useless thumbnail file you can’t delete because you aren’t an admin so maybe all I can do is flag it for “{{speedy|reason}}” (speedy deletion) and “{{Unused file|~~~~~}}” and why the heck is wiki language so gosh-darned mysterious and unintuitive, I guess to keep people not dedicated to it from messing with it). ; D