How do you make banners in MS paint :?

What you mean... with paint, you can do something not so special if you don't have design tablet (and you're bit experienced with it).
But if you gonna do banner with sprites and stuff... then just add them... >_>

But I would suggest to download Gimp (please, use google...), if you don't want to ''get'' Photoshop for free... if you want to do (less or more) nice banner...

And then rape everything in reach. This process is known as "graphic design".

If he want to do sprite like banner or something o__o'

Raping everything in reach helps you get the feel for art.