For me I scroll through the list you get when you first go to find a design and if there are none there I like I go through replica and then racing (if there are no replicas I like). I've found some amazing liveries, my favourites being my Bondurant Camaro Z28, Vaughn Gitten Mustang, Retro Datsun 240Z, BMW Motorsport M3 E30, GT2 Race Mod RX-7, Audi DTM RS5, Mercury NASCAR Cougar, Renown MX-5 ND, Advan Evo X, Red Bull Astra, FINA 595 Abarth and TWR LM XJ220.
But I don't put liveries on race cars.