Many old games (notably Ultima VII) used this ortho 45 degree perspective; it's fairly easy to create pixel art in this style.  Here is a template for making graphics in this style.

The base tile size is 32x32, while the entire tile is 64x64.  Walls are 16 pixels thick, doors are 8 pixels thick.  A table and book are also provided for reference.

If your map needs layers, the walls line up to stack on top of each other.

See the preview below done with Tiled and this tileset.