kkmultes hi, i made the same mistake(well it is not a mistake... is a developer choice that will have impact in the game performance)in my older games in c2, by making huge backgrounds.
Now i use tiled backgrounds for everything that is only visual, take a look at my game"zed-3600"(wip), all the graphics assets in the game doesn't reach 2 mb(they are mainly black), and i have more assets than you see in this video.For instance the sky is a tile with 8 pix width.
[TUBE]http://youtu.be/L_VDlTGTffg[/TUBE]
Gameplay mechanics HD
[TUBE]http://youtu.be/3Gs5mBv3wpk[/TUBE]
Gameplay introduction HD