Tiling Sprites and performance sprites vs. GameObjects

Hey guys,

I currently have a problem I am dealing with. I am currently developing a large game with lots of randomization in it. Kinda like a rouge like game. For that I have a ton of sprites I am dealing with.

Currently most of what I am doing is made as a mix of 3D and 2D (the background is 3D boxes with textures, the player, the enemies, everything else is made of sprites). As I added in coins and other obstacles into the game, my performance went way downhill.

Now my question: For performance enhancement, I want to ditch all 3D objects in the scene and replace with sprites. For the background though, I need a tiled sprite (the size of the background is variable depending on the room). Can you do that or would I need to use multiple sprites "arranged" acting as a background? Also wouldn't that kill the performance even more than a single 3D object?

Hope you guys can help me with it.