A lot of custom skins have been created by LoL players. You can find them on HeroesMod forum
The only problem is the way people used to install those skins needed you to modify your heropak_client and make a backup to be able to patch the game (you had to backup every patch).
But now, you don't need backup anymore if you follow this tutorial!
You will be able to keep all your custom skins every patch without even modifying your files.
Here's the right way to install custom skins:
1. Download the skin (it will be called "Champion".dds)
2. Go to \Riot Games\League of Legends\game\DATA\
3. Make a new folder called "Characters"
4. In that folder, make a new folder with the name of the original skin of the champion
(you can find the orginal skin names in the list below)
5. In that folder, paste the "Champion.dds" skin
For example, a custom Ashe skin would go to:
\Riot Games\League of Legends\game\DATA\Characters\Bowmaster\
If you want to test it out, I put the Ashe skin I use in the attachments. Download the .pdf and rename the "Bowmaster_Clr.pdf" into "Bowmaster_Clr.dds". Then follow the instructions above.
note: The file is in .pdf because the forum doesn't accept .dds files, thats why you have to rename it.
Original Skin names:
-Are you able to turn off the skin when you want?
You have to remove the .dds from the folder.
-If someone has a store bought skin, will the custom skin overwrite that skin with this method?
No, your custom skin will not overwrite a skin bought from the store because all skins have their own .dds files. For example, a custom Annie skin has to be named Annie.dds. If you want to overwrite the Goth Annie skin, your custom skin has to be named Annie2Black_Diffuse.dds.
-Can other players see my custom skin?
No, only you can see your custom skin, unless they installed the same custom skin too.
-I installed a custom skin for Annie, can I do the same for Tibber?
Yes! A custom skin for Tibber has to be named HogyoBear.dds, you have to create the folder "bear" in "DATA". \Riot Games\League of Legends\game\DATA\Characters\bear
p.s. Even if you use Goth Annie skin, you can install a custom skin for Tibber.
p.p.s. This is the one I use: Dark Panda
-How do you create your own custom skins?
-What programs do you need to create them?
The Skinning Start Up Kit
by HappyNihil includes a PDF format Instruction guide and all the tools you need to make your very first skin!
Credits to BananaBoy and Najena