Found this simple but useful sprite maker on a Starter Kit disk by the NorthWest user group of California.  You can create your sprite on screen, then the program will convert it to data statements to include in your BASIC program.  Although it's pretty simple compared to the other tools we have these days, it's completely written in BASIC, so you might find the code useful in the creation of your own utilities.

This archive includes the full NorthWest Starter Kit.  There are some other utilities / programs you might find useful on it.