I was browsing over at the SL Developers community site. I came across a file that Cristiano Midnight posted called SL Clothes Previewer. This software, created by Johan Durant, allows you to preview your clothing and skin textures on an avatar mesh.
You can do this with with the Second Life client, but the preview window is very tiny. Also, you risk uploading by mistake for 10 L$ if you don’t pay attention to what you do. What I like is that you can work on textures during any downtime that SL incurs and still see how they will look.
I found it pretty simple to use. Click the button for each layer and choose an image file. It also supports transparency with TGA files.
Johan Durant asks that if you like the tool, to visit there store, The Motion Merchant, or send a few L$ as a thank you. The store offers a lot of animations. One animation that caught my eye was the trick-or-treat bag. This one is a freebie for halloween, so you better come quick and get your own. It lets you walk up to someone and say “Trick or Treat!”. There character is animated to put candy in the bag that you hold out.