As Reiza have added a few more livery slots in the latest update, I've created some replacements. 4 for the Sharkfin, 2 for the Sigma.
Following some recent feedback, I've also editing the file structure, so unzip the file and drop it into the following:
C:\Program Files (x86)\Steam\steamapps\common\Automobilista 2\Vehicles\Textures\CustomLiveries\