My bike is already small, and its similar in size to a BMX bike. Im just starting to get into it, and I kinda want to make it look and function a little bit better.

And, if possible any ideas on how to make it look cooler?

would help if we knew what the bike was.
try getting wheels with a high number of spokes (40+) as these are usually seen on bmx’s. maybe remove the front brake and get a short stem, handlebars with a big bend in them. if you have three chain rings on the crankset, perhaps change that for a single chain ring crank, and stick a single speed sprocket on the back, rather than a gear cassette. that way you can remove any gear cables/shifters. bmx’s usually have a rigid fork on the front, so look into getting a rigid jump fork rather than suspension. lower the seat. maybe some of those funky retro bmx grips with the big rubber disc on the inside edge.
thats the best i can come up with from my imagination as i don’t know how your bike is set up.