Note the trees are borrowed from Jim Pearson's Isle of Man circuit (and then I fogged them up) so thanks Jim
Considering it's another one of those hex-editing jobs I didn't bother to really perfect it at this stage so I think there's a lot more that can be done, maybe not just fog/mist.
The method is a simple cut-and-paste one, whereby I created all the sub-images seperately in PSP, converted to mips and then cut the BMAP section and pasted it into the relevant BMAP part of the 'main' mip. I think being able to control a mip's sub-images has some possibilities but it's a bit of a pain doing it all in a hex editor...So what I could really do with is for some clever chap to write a program that could maybe automate the process, something like loading e.g asphalt_sub1, asphalt_sub2, etc and then saving as asphalt.mip with all the chosen sub-images. Is this possible? I wish I could do it myself but my programming skills never developed any further than ZX Basic...