-Documentation can be found at http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/bitmap.htm .
A bitmap is monochromatic representation . Use photo when you want color images or icons (aka a pixmap).
"How to edit an executable's desktop icon"
Sometimes people want to know how to edit an X bitmap or to create a new one. See Paul Obermeier's http://www.posoft.de/ 's poBitmap, part of poSoft utilities for one tool.
KPV See Bitmap Editor for a simple tool to create and edit bitmaps.
Another Tk-pertinent sense of "bitmap" is as a permissible argument to specific canvas subcommands. A model of such uses is
.canvas itemconfig rectangle -stipple $bitmap
While Tk offers many interesting bitmap capabilities, it can be difficult tracking down their documentation. A good starting point is the distribution man page for the library entry point Tk_GetBitmap [L1 ]. Along with much else, it provides a list--"error", "gray50", "question", and so on--of standard bitmaps built in to Tk. Apparently Tk provides no script-level introspection to access this list. To see these built-ins, therefore, it's necessary to perform something like
Tk syntax help - Arts and crafts of Tcl-Tk programming [ Category Command | Category Graphics | ]