how do i veiw skins in wc3 veiwer?

I know how to veiw flat .blp files in wc3 veiwer but, is there a way to look at the models with a custom skin?

download the latest version of the Warcraft 3 Viewer (on that site, download section), and to view a BLP simply select the BLP in the treeview or open it with the file->open menu.
To use custom skin, go to the Current File -> Remap textures menu, after having loaded the mdx you want to reskin.