I'm using beta 28 and I'm having problems with the banners - so far only for SNES games. NSUI won't download the images, so I use SNES9x on my PC, take a screenshot of the title screen, and upload that in for both the icon and the banner. It looks fine in the injector, but after I make the .CIA and install it, it looks like maybe the image wasn't big enough? The icon is fine, but on the TV in the banner, it just sticks it up in the corner, and the rest is all red. I've tried making the image bigger(@ 2x, 3x and 4x), but the same thing happens.
EDIT: It also doesn't play. I run it, and after the initial 3DS screen it just goes to all black screens and locks up the system. I have to turn the 3DS off and back on again.