Alot of people think you need to use textures, power of 2, in Sketchup... Really, you dont have to, it's just needed for the sake of importing anything into RCT3.
I've used many non power of 2 textures in Sketchup, but then resized it to the power of 2 for the importer.
It is helpful to use a power of 2 texture, saves one less step to do for importing... but at least in sketchup, i know im getting the true texture desired and not having to skew or reshape the image!
Now when i make my own textures, i make them either 512x512, or 1024x1024.... this way i can get my image to look right in game... if i make them 128x128 or 256x256.. then having to size the texture larger on my object can get a little pixelated... if i stay at a larger power size, then scaling the texture smaller wont lose or distort the image! I know it may be a bigger file size, but at least i know you'll be able to see and understand what the image/texture is...than to try and figure it out..and be blurry!