What file format are textures in Second Life?
Textures in Second Life are in TARGA (an acronym for Truevision Advanced Raster Graphics Adapter) format (with the file extension .tga)
How to save to disk a texture from your inventory
You may sometimes want to edit a texture. Locate the texture in your inventory, open it in-world then go to: File, then to: Save Texture As … Give it a filename and click Save. After you’ve saved on your computer you’ll undoubtedly need to resize it … but it will be a perfect copy to work on. Edit it in GIMP or Photoshop, or any other image processing application that can read and save .tga files, then upload it back into your inventory.
Download further textures (individually, or 10MB in a single download) from the extensive Second Life library of textures at:
Masses more free textures from Daiki:
and free shirt and clothing textures from:
Free Second Life Shirts
Nicola Escher’s ‘Alpha Channel Primer: Transparency in Second Life’
A good introduction to alpha channels and transparency.
Robin Wood’s ‘Alpha Channel Discovery’
Not quite as perspicuous as Nicola Escher’s tutorial, but covers topics omitted from hers