Radical Silvertone amp modifications are not nearly as frequent as guitar re-workings, due to the fact that there's electricity flowing through those things, and that amps tend to be kind of in the background, anyway.
Visible mods, when they do occur, seem to be limited to re-covers, re-grilling, and the odd paint job. Internal mods, like rewiring, or adding a master volume or the like, tend to be far less visible and usually carried out by qualified technicians.
The most visible amps mods are of course, the entire re-enclosing of the amp in a brand new housing.
We've got plenty of examples of visible modifications, so click away!