Wow, this is really simple. Just create some rectangles, load all these textures and place them onto the rectangles. You will find all the necessary knowledge in
XIN.
Please also checkout the xith-tk project from SVN (and of course the xith3d project itself). It contains a lot of testcases and demo code. Read
this at the bottom of the page.
If you have any performance issues with this solution, which I don't expect, we can tue it by merging many of these triangles to one geometry and placing many of these images on a single texture.
The UI can be easily implemented using xith's HUD system.
Marvin