Well the first thing you need to do is download Dr. J's Object Creator, i find it kind of hard to find it on the web so ill post a link
http://rapidshare.de/files/6561805/RCT2objectEditor123.zip.html
A small tutorial:
Then you need to create a NW, NE, SW, SE views of what you are creating. Or you could create one view and rotate it. Make sure the picture that you make are in Bit-map file format!!! Usually when you rotate it it turs out a little better than when you dont. This is because the size/colors are the same. You can edit it in the window. Its a pretty basic program after you get the hang of it. After your done editing click the description button ( it looks like a pencil ). Fill in the information for American. Then go to edit tab and click copy to all other languages. Save as a .dat and put it in the folder
C:\Program Files\Infogrames Interactive\RollerCoaster Tycoon 2\ObjData
Then you have to go into RCT2 and go to custom scenery. Now I'm not sure what exactly to do, but I think it is pretty simple. I have not created any scenery for a
LONG time.
Hope this helps!