Gift ideas for two brides

Ok, so my ex sister in law is getting married to her long term girlfriend(8yrs of dating!!!) They are having a Halloween wedding, they are Roller Derby girls, they love animals(they have 11 pets of different kinds!), their are into goth/rock music, LOVE halloween. I just want to know what can i give them as a wedding gift, I wanted something cute like the him and hers gifts but in a hers and hers kinda thing, something that they will like and use, they don't cook much so idk what to give them, i love cooking so pretty much every present I've given has to do with the kitchen. I'm at a loss, do any of you ladies have any ideas on what could be a good present for them?

-TIA

**Update***

You all have very good ideas!! Makes me wanna get them everything!!! Lol knowing me, i probably will!!!!