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I might question adding the same keyword with just a number as an ALT tag to the images might be flagged as keyword spamming. If you have a full page (gallery) showing 20-50 dresses to the user all at once, you'd also have 20-50 ALT tags that are basically the same. - So I'd suggest watching out for that issue. Perhaps you can tell when reading from a database, how many dresses will be appearing on screen and then just program it so it shows the ALT tag on only 1/8 of them or 1/4 of them, or whatever works out proportionally.

If you have old wordpress databases sitting around, it would only be a problem if you still have the WP that's connected to them still around also. If so, anyone (or a bot) that visits the old installs would be pulling data from the DB and thus draining a small fraction of resources away from your current install of WP. This shouldn't be a problem, considering you mentioned they are experimental and I assume are not in production. The more pull on the database, the more bogged down your server could become at a given time; usually not an issue unless you get sudden spikes of traffic on your experimental WP installs; which would slow production WP down. Hope that made sense.

Really doubt GoDaddy will give you a refund. If you do absolutely nothing with them, I doubt you will be sued just for owning them. I wouldn't bother bringing the issue to the companies attention at all; you may be on their radar then. Personally I'd use them for legitimate purposes like creating fan sites; but would keep advertising and any money-making schemes off the sites for at least several months. Build some social media pages for them and make it like a real fan site. That way it will be less-likely they come after you later on saying you were just trying to make a quick buck. Do not put a phrase on the sites saying "buy this domain name" or anything like that.  Just my 2 cents (* not legal advice)