LFS skins are JPG files. If you already are adept at using software like Photoshop then all you should need is the knowledge of a few "tricks" like
compensating for stretching.
Something else that may help you to save a lot of time is the Master Skinnerz
kits, which are PSD files containing accurate templates and wireframe guide to help you with wrapping and placement of graphics like logos.
It is also important to know that you can upload skins to LFS World so that other licensed users can download them in-game and therefore see your skin online.
LFS World skins need to be 1024 x 1024 pixels and no larger than 400KB (else they will be compressed by LFS World, which is something you should avoid).
LFS World also resizes skins to 512 x 512 but locally you can use larger sizes like 1024 x 1024.
Many skinners create their skins at 2048 x 2048 pixels before resizing them down to 1024 x 1024. Creating skins firstly at the larger resolution helps you to achieve better detail even when resizing down to 1024 or 512.
You can use our
skin section on these forums to display your work or get opinions.
Good luck and have fun!
