Sorry for the delay in responding, but I wanted to ask your question of both the CAT and TG Committees to provide a balanced response.
In regards to possible software to use when producing graphics, there are several options available, including but not limited to: Inkscape (.svg files), CorelDRAW, Adobe Illustrator, Microsoft Word, and Viewplus' Tactile Software Suite (TSS). Each has their own merits in regards to which type of graphics you will primarily be producing (technical, literary, etc.). The major thing both committees wish to stress is to base the creation of your graphic (software used) on the output method (embosser).
As for preferences for TGs produced using different methods, these will vary based on the experiences of each individual braille reader. Some prefer graphics produced on a braille embosser and enhanced with collage elements, while others prefer SwellBraille or simply the unmodified dots produced on an embosser such as those produced by ViewPlus.
Both committees encourage you to discuss with your student(s), if possible, the methods preferred for graphics production and go from there.
I hope this helps!