I'm not seeing anyway to get rid of carts once they are uploaded. I accidentally uploaded a wrong version and then have been trying to find a way but I don't see it.

Are they just permanently on here?

I don't know if this will help you, but when I was updating Tiny Tactics, which was already at version 1 at the time, I accidentally submited my .p8.png twice (therefore getting versions 2 and 3).

I inserted version 3 on the game's post. Then I went to Submit > Update an existing cartridge, just to check what really happened, and version 2 was there, under "unlisted carts". Versions 0 and 1 weren't, though. Somehow the BBS knows they have been in a post, but have been upgraded, so it doesn't list them anymore.

I tried inserting version 2 into a comment, but it didn't help. As soon as I deleted the comment, version 2 went back to the "unlisted carts".

The solution, at least for me, was to insert version 2 in the game's original post. Once I removed it from there it disappeared from my Submit > Update listings. Somehow the BBS now knows it has been updated.

Now my Submit > Upgrade screen only shows version 3 under "listed carts", as I wanted it to.

I hope this helps!