DS icons look crappy anyway, especially on 3DS, low resolution picture and all...so...
Can we make our own banners, and how?
I managed to make one for a game im making on Unity, but let me tell you the process is a pain in the ass, and sadly i didn't find a simpler way.
You need to sign up as a nintendo developer to get the developer kits, these come with a bunch of files and softwares, one of these is like a simple little 3D enviroment where you import your models, set up a bunch of things, and export.
But to create these 3D models you need a plugin for maya or 3dmax. To texture these models you need a plugin for photoshop that lets you export in Ctex format. And after exporting you need to convert that file to .bin or whatever this software asks for. It's very complicated and not worth the trouble unless you're making your own game i suppose.
Edit: nintendo dev kit provides the maya/3dmax and photoshop plugins, but to convert from Cwhatever format to bin, or to Cother format, you're kinda on your own, depending on software shared by some people in this forum, which did help me a lot.