It's the tiles, scenic objects and background sprites (none bigger than 64x64) that make up most of it.
But 3000+ is excessive. I presume you have a new object for each title/scenic object etc which is the wrong way to do it.
You only need 1 object for title and multiple instances.
Spritefonts are better for titles. So 1 object spritefont, unlimited titles.
You can have multiple instances of objects just drag them out.
I once saw a guy build a whole checkers board. Each piece was a separate sprite. When all he needed 1 sprite with 2 image frames.
You won't get performance issues per say, but will increase your download, but more importantly, editing 3000+ objects and you will be editing, over and over and over and over etc
Make life easier