Base textures, and 3D mappings, as simple as that. Some vehicles are a joy to mod, like Churchills, Cromwells, Lloyd carriers, even Stuarts, summing up,...all pure british (not Lend Lease, not ported form CMBN v.1.0 and colorized ) vehicles are to my taste the best made textures along with some german vehicles (specially in CMFI), but ALL Sherman based textures (shermans, sextons, etc) are NOT nice to mod,...It happens with other vehicles too,..but I found that overall, german vehicles and pure CW vehicles are much enjoyable,...Shermans, even in CMFI they are still not enjoyable projects. SO I tackle them with lazyness,...still, they have so many decal options,...If I was to choose one vehicle for modding starters I would say,...pick up the Cromwell. Trucks and jeeps are not vey enjoyable either,...Vehicles with rounded shapes are harder than vehicles who have square surfaces (M4 Early against a M4A1 as textures stretch,..), so if you want to to start modding pick a vehicle with many horizontal and vertical surfaces.