I haven't seen this question posted, and I can't find any answers on google, so I figured I'd ask. I have a LOT of left over cake (lots of crumbles too) from a previous carved design. I know you can add icing and make cake balls, which I might do, but I am  also wondering if I can somehow make it into another cake? I must have like 4 tubs full of cake, lol. Answers appreciated :)  Thank you. 

Or cupcakes or something other than cake pops. 

I wonder if you could add a little fresh batter of a contrasting flavour (eg. if you have chocolate add vanilla) and bake it that way - people do it all the time with different shapes like circles etc in cake so I don't see why it wouldn't be worth a try.

You can easily do trifle cups or a big trifle bowl, bits of cake with sweetened flavored whipped cream, or smbc, & fresh fruit or pastry cream, or pudding.

I second MBalaska's suggestion.  Recently I used left-over frozen cake domes and frozen American buttercream and created a "bowl cake".  I used a large glass bowl and layered chocolate cake, peanut butter buttercream, chocolate cake, oreo buttercream, chocolate cake, and topped with ganache and chopped pecans.  I provided paper bowls and a large scoop and told everyone at the party to dig in. 

Years ago before I knew how to bake a flat cake I had a lot of carrot cake tops from when I made my wedding cake.  I didn't want them to go to waste so I layered the tops with frosting and more tops in a pan and made it sort of flat on top with more icing on top.  I came up with some weird name to make it sound like it was fancy and everyone loved it at work.

The second use up scraps tip (second generation cake) talks about using scraps in a new cake mix.

http://www.wickedgoodies.net/2012/09/what-to-do-with-leftover-cake/