It is possible to do animate textures, but you'll have to code Lue to do the animation. As for how to do the HUD art, check the thread in this forum where Havoxx was working on the tribal HUD... for that matter, have a chat with Havoxx since he's already done it and have a look at his tribal HUD plugin.
What people don't get is that I am, ultimately, an artist at heart. My brush has two colors, 1 and 0, and my canvas is made of silicon.
Let's work my majik here on the keys. Basically, all you want to look at is in your interface\addons\nui\layouts\default\hudlayouts\ and well, I'll leave you to the LUA, in each LUA, there are lines that look like this...
The underlined bold, that's what you want to look at. Essentially, you adjust those files, and rename them, the min offset is the 0 point of your skin, in other words, the very bottom you want your skin to start at.
This is a very tricky one to do, you need to do it properly, and essentially, after you have your art ingame, you need to adjust them. For me, since my tribal hud is shorter, I needed to drop the max offset to .5, since my hud is about half the size of the original.
I won't tell you it's easy, the graphics and offsets aren't any work essentially, it's making graphics and simple trial and error. Here's where the fun stuff comes..... in those same files, there are lines that read like this.
Those are the text blocks, I'll leave that to you, essentially, the relative_to you don't touch, the offsets are the main ones you need to modify, I find setting the Anchor_pt and relative_pt to center, are the easiest ways to start, and work for there.
This is as far as I can go, I hope I helped you, but I don't know how to explain it any more, good luck.