Hiya Wulf, It would only be the landclass and waterclass .bmp's that are 256x256 sq. in your Scenedb/World/Textures folder.
And remember to check the ones in the CFS2 Root/Texture folder from when you had copy them over from Scenedb for the add on runways. They should be 86.4 kb.
The vertical black line (blending textures) and the 64x64 and 32x32 smaller .bmps should be fine. No need to check these...usually, since they are never changed through addons. Do Not change anything in the addon scenery folders such as MR Papua New Guinea > Texture. That could cause a heap of trouble.
Please see the piccy.
Hope this helps, Dave