To add new playermodels to the shop from workshop, simply install the workshop addon to the server collection ( see GMod wiki). You can then pick a playermodel and change bodygroups and skin, if the model provides them. Click on the playermodel preview to bring up the selector. To create a playermodel simply go to Mangement -> Create Item -> Playermodel. The last step is to move it into a category, which can achieved via drag and drop. Once happy, save the item and if successful, will be found in Uncategorised Items, located inside the Manage Items tab. Hover over them to play an animated preview, which will give some indication of how they look in-game. This will bring up a box displaying all functioning materials inside /trails. Once you are happy with the name and price, click the image preview next to the file path. Go to Trail to bring up the basic settings menu, where you can personalize the item you are going to make. Now you should be on a tab called 'Create Items', with options to select the type.
To get your image to an actual Pointshop item, go to the second tab called Management.
'$basetexture ' 'trails/dollar ' '$vertexalpha ' 1 '$vertexcolor ' 1