Excuse me if this is has been done before, I did search the forums before posting but came up blank.

I  have a bit of an odd request. I'm writing and self-publishing a book about motorcycling skills, and have been thinking about ways to produce some simple diagrams to illustrate points in the text. My own graphic skills are nudging zero, I can't afford to pay a graphic artist, but looking at some games it crossed my mind I could use isometric map elements to design the items I need. 

Ideally, I'd like a simple drag-and-drop style map editor or a simple graphics program which will quickly allow me to build up mini-maps of 20-30 tiles which I can then save as a graphic (even a screen grab will work) that can be dropped into the text. The ones I've looked at seem to have quite a steep learning curve, as well as graphic formats that I'm not familiar with. 

Any ideas on what would be dead easy to use?

Thanks in advance.