No need to do much for enlarging a room or create perspective. You just have to know how to use paint to transform your interior. Here are some ideas for using optical effects properly:
Light Colored Walls & FloorsLight colored walls and floor would have an enlarging effect and would also enlighten the room. You'd better chose one color only from floor to ceiling: it won't draw attention to the corners, the room will then seem larger. Light teints (wood, white, light brawn) would also perfectly match with colorful furniture. 

Dark floor, light wallsA dark floor would make an enlarging effect and give more character to your interior. That is the reason why it is mainly advised to have a floor slightly darker than walls. Grey or black floors can be very elegant but they would also draw attention on the floor only, overlooking the rest of the room. What's more, pay attention to colorful floor, your eyes might get tired of it very quickly! 
Light floor and dark wallsDark walls - with light floor and ceiling - would seem higher and deeper but also very tight. You should also have a very bright room if you want to use a dark painting, so that your interior doesn't seem too dark - pretty much like a shady basement. 

Light floor and walls, dark ceilingA dark ceiling would make the room lower. Nevertheless, if you have a high ceiling, painting it might be a good idea, it will give the space some colorful energy and transmit light from the different ceiling ...