Hi and welcome to the forums
I'm glad to hear you're getting things ready in advance so it's not an impulse buy! Having said that, quite a few things pet stores sell aren't good for piggies (they will sell anything to make money!). A few things they sell you shouldn't use are wheels/exercise balls/leashes, mineral or salt licks, yogurt treats and chewy treat bars. If you bought any of those you shouldn't use them as they can injure or make your new piggies ill. You might be able to get a refund if they are unused. Did you buy a cage at the store? They are really too small and your girls would love a C&C cage. The home page of the site is full of ideas, as are the forums and Photo Galleries.
Anyway onto your actual question! You can find lots of cool things for your pigs yourself for free/cheaply - cardboard boxes, paper bags, piles of hay, toilet roll tubes and bricks to climb on. You can also buy pigloos, plastic stools for hideys, plastic or cardboard tubes and some pigs like cat or bird toys to push around or jingle. Also, lots of pigs like fleecy cozies which you can make or sew yourself (instructions are here:
https://www.guineapigcages.com/forum/accessories/17507-how-make-cuddle-cup-requires-sewing.html )
Hope this gives you some ideas!
