I was wondering if I'm alone in my thoughts about what to create to upload to stock.

What I usually do is compose a set of images based on one theme.
My themes are usually based on business, internet, and current events.

Cranky MIZ
The voice of reason

I too base my images round a theme, about a set of 10 images then move on to the next theme. After about a month I go back review how well the images have sold (or not) and see if I can improve on what I have done or expand on the theme (or just drop it!)