Any idea or link of how to declare / use a particular image or icon to represent a custom or commonly used class / object in U.M.L. (Custom U.M.L. extension), not just “<< my stereotype >>” ?
By example, U.M.L. 2.* has custom images for 3 – layers methodology:

To my knowledge there’s no formal and/or standard way to define custom representations in the language itself. There are tools which support it (e.g. MagicDraw, Rational Rose iirc) but the mechanism is tool-dependent.
hth.