I know that the OHV means overhead valves but what exactly is a L-Head engine?

The only thing I can picture is that the L-Head engine is simliar to the old flathead v8's of the 50s like the ford or the nailhead buicks of the same vintage.

Does anyone have any good pictures showing the differences?

I do remember several years ago when I took my old 12hp engine apart, the head had no valves in it.

you are correct..... its like a old ford flat head......, the valves are beside the piston... piston is flat headed (like a pancake)...
L heads are called everything from l head, to side valves, to flat heads....