"cartexture" query
You can edit the existing cartexture files pretty easily. This will retain all of the detail such as blemishes and textured pieces as a plus. Just locate where these are stored on your computer, make a copy, and place that in your park folder, then you can edit away in your favorite photo manipulating software. If you have steam, just right click on the game in the library, select properties, then local files and browse. The folder should be there.
A little more info, and I'm no expert here but this is my experience, you'll notice several different files for each coaster type. The important ones are "cartexture_01.png" and "cartexture_01_colormap.png"; you may also have a "cartexture_02.png" etc. for types with a zero car. The cartexture is obviously the file that you see wrapped onto your coaster cars, it'll have the NL logo on it. Edit this file 'til your heart's content, then have a look at the colormap file. Just looking at the files side by side, we can see black outlines for all of the details and the NL logo, with gradients elsewhere. Black on the colormap will preserve whatever is on the cartexture file while white will show the color you pick in the NL editor with the gradients being somewhere in between. You should be able to work it out from there, depending on your understanding of PS/Gimp/whateverelseyouuse.
Also, there is a pack out there with all of the textures with the logo removed, however the link doesn't seem to be available.
Thanks for the response. I AM getting my picture on the car, but it's just a small segment of it - a bottom corner. My problem therefore seems to be one of "scaling". I'm quite happy with picture manipulation, and have reduced it several times till it's 5% of what I started out with. However, it still displays the same. Is there some "no. of pixels" rule, perhaps?
I'm attempting something new (for me) - cutomising trains/cars. I want to attach my own pics to a train/car. I've had a dabble for a few hours but things aren't turning out like I expected! For starters, I've tried. jpg and .png images. Does it matter which? Secondly, the pics I've tried seem too big. How do I get it so it fits completely on the front of the train? Sorry if this is a bit basic, but I couln't find any related detail about it anywhere. Thanks.