Welcome princenoire. Tony's given you the best source - Paul's images are all under copyright so you do need to contact if you'll be using his work on something as prominent as Wikipedia.
There aren't an awful lot of images of Mustrum out there and of those most of them have him with the rest of the faculty of UU. If you do a Google image search (on Mustrum Ridcully) then you can get an idea of the range, which for wiki I would say needs to be either from Paul Kidby's portfolio or of Joss Ackland playing him from one of the films (on Sky presumably).
Glad to see you know of the need to acknowledge copyright
here's a link to Paul Kidby's own website
- it's better to use his site for this rather than PJSM Prints as that is now a licensed shop outlet for his earlier work and doesn't have all of Paul's later work. Provided you aren't
using the images for commercial purposes, Paul is happy for people to use his images under the 'fair use' clause of international copyright for the internet (see this page
as to what usage he permits and how to acknowledge him.
If you want to use something you find using a search engine - when I do this I make sure to get the website and/or artists details if I'm using them for reference or illustrative purposes with a tag such 'Mustrum with permission of...Paul Kidby/Sky TV etc' or similar. In the UU group illustrations Ridcully's generally the tallest and 'sportily' built
, in the centre and has a very full and usually circularly trimmed beard - for the Unseen Academicals pictures he's the one not wearing a pointy hat with a black eye