IceWM scans the theme and configuration directories for a subdirectory called cursors containing monochrome but transparent XPM files. To change the mouse cursor you have to use this filenames:
Default cursor (usually pointer to the left).
Menu cursor (usually pointer to the right).
Window movement cursor.
Cursor when you resize the window by top left.
Cursor when you resize the window by top.
Cursor when you resize the window by top right.
Cursor when you resize the window by left.
Cursor when you resize the window by right.
Cursor when you resize the window by bottom left.
Cursor when you resize the window by bottom.
Cursor when you resize the window by bottom right.