It is possible to apply one image to several different objects. First you load the image using
load image and then apply it to the objects using
texture object (but I think you already know this).
If it isn't working, then it might have to do with the UV data of the object being incorrect. If the object just stays black, then perhaps the material of the object or the normals are messed up. Use
set object light to check whether or not this is the case.
There used to be a limit of 65535 images. But I'm not sure if it still applies. But as you can see, 65535 images should be more than enough for any game. The chances are higher that you would run out of memory instead of running out of image numbers.
Bitmaps should not be confused with images. They are treated differently and have other options which is why bitmap numbers are capped at a lower limit. If you want more information on bitmaps, then try searching the forum.