The term pixmap is often used in contrast to bitmap, to indicate an image with more than monochrome colors.
The word is often used to specifically refer to X11 pixmaps, i.e. XPMs, which are surprisingly hard to display in Tk... you'll need something an extension such as Tk_Xpm, Img or XPM to photo image to do so.
It would be nice if Tk some day had the support added.