For me the main thing would be spoilage- off odors, or when you thaw them, if they're falling apart (as they will be if they've been thawed & re-frozen)- sometimes the hair may easily fall off (especially from the rodent's belly) & the belly may appear dark colored- gag! -that's spoilage.
Rodent feet are small, as are tail tips- so when frozen they're fragile & easily broken off- not any big deal at all, quite normal- no one bubble-wraps their rodents to keep feet intact.It would be very expensive if they did.
Malformed- use your best judgement, but I think "extra feet" would be extremely rare, & not something that would impact the nutrition either way. Extra feet are certainly not "contagious", lol- but I've raised rodents literally for decades (zillions of them!) & I have NEVER seen any with such defects. Post a pic if you do.My guess: most likely, the rodent got squished while packing before it was frozen solid, so it came out looking weird, though it actually was normal.
Sometimes from the quick freezing process a little bleeding will occur from broken blood vessels in the noses- normal- but you don't want to see animals that look like victims of torture or with smash-type injuries- if not spoiled, it won't hurt if they're fed, but personally I'd not want to support anyone treating any animals that way, so such evidence would matter to me when I decide who to support (buy from) -if I weren't raising my own, that is.