Well you're only limited by your imagination; I've heard of blue cheese pear soup and I've not come up with any feasible way to approach this, alas.
Good soup always starts with a good base, the base being the liquid. Now, I try to avoid using just plain old water as much as humanly possible. This may lead to more time consuming recipes but the ends, in my opinion, justify the means.
This brings you into the realm of 'stocks'. Personally, I don't like the store-bought stuff because I find that it's ridiculously salty (just as well, they need to preserve it). By all means, it's usable. If you feel daring, look up a stock recipe (that's chicken, beef or vegetable) on the interwebs, mind you it is time consuming to make (approximately 2.5 hours).
So now we have a base, we need to pick flavors. Pick any flavor under the sun, think of the way to make it taste best in a soup (keeping in mind that water will dilute the flavor), and think of a way to add it in.
I want a sundried tomato soup.
Vegetable base will work best. The sundried tomatoes in olive oil will just be weird and oily in the soup so I'll use the dried ones. The dried ones have a chewy texture so I'll simmer them in the base so they leech out their flavor. I'll add some tomato puree to enforce the tomato flavor, but not too much that I'd overwhelm the sundried-ness. I'll puree the soup with some dried sundried tomatoes for texture so I dont need to add noodles. Maybe I'll use some of the oil from the oiled sundried tomatoes to make little croutons to decorate my soup. Salt+Pepper and we have sundried tomato soup.
Clear as mud?