Beetle skins act very similar to Custom Decors. You can find the Beetle Skin Maker in the Oasis for 5GB.
Like Custom Decors, you have to draw the skin, or commission someone to draw it for you, and then submit it to be accepted. Once it is, you will receive 5 copies of the skin to use or sell as you wish.
Each copy can only be used once, and will ‘die’ with the beetle. It can be unequipped, however this means that the skin is used up, and cannot be re-equipped to another beetle.
Skins are found in Branch Sales, under the search option for Custom decor.
Once equipped, beetles will display the skin’s name, and their image will change to that of the chosen skin.