How can I make my guinea-pigs cage more interesting?

Try adding some new toys, my guinea pigs LOVE they're little toys. A favorite of there's is a little wicker ball with a bell inside, they like to roll it around, pick it up in their mouth and throw it, and it keep their teeth at a good length. Good luck! :)

Put some things, to chew on, hide in and run about, also put something in there so they can cuddle, like a blanket...or towel, or small dog bed.

Put little toys in it, or get a snack shack. Snack shacks are homes and food! My pets love them!

Check for the guinea pigs information if they are poison to anything so you know what not to use. If food coloring is safe take the little pigs out and paint it with food coloring and let it dry. Then play with them for a while. Once it dried make a tunnel out of finished toilet rolls. Then paint with food coloring if you want to. Next put some cookies and let them eat. Then just buy alot of toys and put them in there.