Graph paper or grids
I did some searching, so I know the subject of grids and/or graph paper has come up in the suggestions forum before, but I wanted to add something to the idea.
I've been teaching myself figure drawing, and one technique I've stumbled on is to lay a grid over my sketch page (as a tracing image) and then bring in a reference image with a matching grid overlaid. Doing this lets me easily check the proportions of my drawing against the reference image while still allowing me take advantage of the ability to rotate both the sketch page in ArtRage and the reference image on the fly, as well as zoom in and out on both.
Doing this in ArtRage does require that some preparation work though. I like to work from large to small details, so I have set up five different grids for my sketch page - 5x5, 10x10, 15x15, etc. Then I have to set up five different versions of my reference image with the matching grids overlayed. Fortunately, I have graphics programs that let me do this prep work without too much trouble, but it would be so much nicer if I could set up the appropriate sized grid for both my sketch page and the reference image in ArtRage itself.
Anyway, just a thought.