My commission rates tend to be 'ballpark' rather than fixed, because the final fee depends on how much work is done for a particular piece, but here's a guide:

8.5" x 11" -- minimum $10 for a basic b/w sketch, $15 for two colours, $20 for colour

11" x 14" --  minimum $20 b/w, $30 two colours, $45 for colour

16" x 20" --  minimum $40 b/w, $60 two colours, $100 for colour

larger work -- negotiable

B/w or Monochrome Media: Pen/ink, Wash, Graphite, Charcoal, Conte
Colour Media: Coloured Pencil, Watercolour, Acrylic, Marker, Mixed Media, Digital
 

Pencilling: minimum $20/page, rate may vary based on degree of finishing.

Inking: minimum $20/page, rate may vary based on degree of detail

Pencilling & Inking: minimum $35/page, rate may vary based on degree of detail 

Washes or Continuous Tone Art: minimum $50/page, rate may vary based on degree of detail. Page 
size may be larger
 

The fees listed above would be for work done and not for all rights. Unless we negotiate otherwise, I retain all rights to what I create. The fees for for-hire work would start out higher as the rights are being sold as well.