Does anyone know of an app for my desktop to be able to draw on a photo in another program - like picking up a pencil off the desktop and drawing on the photo while staying in my working program?

Hi bracesonbracerd,

Welcome to the Apple Support Communities! I'm sure we can help you out with your question, or at least get you pointed in the right direction. I'm a bit unclear on your specific use case, but if you are simply looking to annotate or mark up an image, you can easily do so in the built-in Preview application. You may find the information and steps outlined in the following article helpful:

Preview (El Capitan): Annotate an image

Regards