[Leica] Need pricing info/advice

[grduprey at mchsi.com (grduprey at mchsi.com)]

Today I was approached by an artist who wants to use one of my Eagle photos, 
the image of the eagle, in a piece of his art.  He is asking for the 
electronic file, and I'm not too sure this is a good thing.  He has asked 
for me to come up with an appropriate amount for compensation.  I'm not sure 
how to charge for this type of use.  Has anyone done this type of sale or 
have any idea of how to figure out a price?  The two images he is 
considering are shown below.

http://gallery.leica-users.org/v/GRDuprey/Fish+in+tow2.jpg.html
http://gallery.leica-users.org/v/GRDuprey/Reeling+it+in2.jpg.html

Any help/advice would be appreciated.

Thanks,
Gene