Xterm, and likely many other X11 programs, do not set themselves
window icons, which window managers typically use to represent that
program window in switcher lists, taskbars, and so on. This program
can set the X11 window icon for any given window, to that of a given
image file.

usage: xseticon [options] path/to/icon.png
options:
  -name     : apply icon to the window of the name supplied
  -id   : apply icon to the window id supplied

Sets the window icon to the specified .png image. The image is loaded
from the file at runtime and sent to the X server; thereafter the file
does not need to exist, and can be deleted/renamed/modified without
the X server or window manager noticing.

If no window selection option is specified, the window can be
interactively selected using the cursor.

Hints:
  xseticon -id "$WINDOWID" path/to/icon.png
Will set the icon for an xterm.
