For some design I was working in dimetry, depicted with this image. Dimetry refers to that two of the axises scale factor is the same. That description covers a large variety of axonometric views though. The scale factors and the angles I chose result that if you mirror the y axis along x axis, you will get z axis. There are similar dimetry-s that are used more often, like the so-called conventional axonometry. Here is an image of that (original author unknown). Another commonly used one has it's axises at 97°; 131,5°; 131,5°, and some may even use different scale factors too. To me this one seemed a more trivial choice. Image drawn with inkscape. There are three invisible planes included in the svg, to make mapping of objects easier.