To keep things simple, I'd do the following:

We assume as a starting point something like your target tile shape at the top - a 1-bit bitmap which I assume tesselates correctly - if not, get the tesselation working first.

Create a `Tuple<float, float> array[64][31]` reflecting the target pixels. Each such array cell is a UV coordinate (0.0->1.0 exclusive range) into any existing image you'd like to project into isometric space. For cells that aren't part of the tile, just use e.g. `Float.MaxValue` for x and y (and remember to check for those and skip them when processing - see below). For all valid cells, read on.

Populating valid cells is a matter of using a mapping formula from iso to ortho space, i.e. "for some isometric [x,y], what is the corresponding [x,y] in ortho space?" - this allows you to get the texel you want at the position you want it in the iso tile. There are plenty of posts around on isometric conversion formulae, see for example [this answer](http://gamedev.stackexchange.com/questions/30566/how-would-i-translate-screen-coordinates-to-isometric-coordinates/30574#30574). The end result is essentially that you will map every isometric-space tuple to an image-space UV coordinate.


Once you've populated this conversion array with the mappings, you could write a nice wrapper function that uses the mappings for any tile that wants to populate itself from an image:

    tile = new Tile();
    tile.FromImage("/images/myimage.jpg");

...which will run through the isometric array tuples and pull the corresponding coordinates from the named image, and possibly apply some smoothing / subtexel sampling.