Hi-res:
AH tops out at 512. This is to save bandwidth sending the installer files to clients, and to let people download them faster. Even if you set at 1024 it's still 512, from what I understand.
Installing the high-res pack merely upgrades the textures to 1024
- so that when you set to 1024 you actually get it. From there textures are down-sampled when you set to 128, 256, or 512.
[* = certain old textures, like the 109E and the d3a1 val, don't have default 1024 textures even with the high res pack, as they never had default 1024 textures. The custom skins may be at 1024, however.]
Skin Viewer
The skin viewer is separate executable, but it's a small one. The skin viewer is specific to each patch of AH2, so you may need to upgrade it every new patch that comes out (I think 2.05 uses the viewer from 2.04, *I think*). In it you simply have a plane showing, and you have sliders and options to the right. You can spin the prop or stop it, move gear, flaps, flight controls, etc. In the new models you will be able to enable add-ons and external hardpoints (check out the 190a8 for an example). Select the drop down box on the top right to choose your plane. It may take a second to load. Click and hold, and Right click and hold, will help you change your view. Play around with it.