Don't worry, you're certainly not alone!

Lots of people, including me, have the problem of boring dreams, and it's not necessarily anything to do with your imagination. There are some things you could try. Firstly, you could look into dream incubation, which is where you do things during the day to help you dream about a certain subject.

Another thing you could try is changing your daily routine. A more varied and interesting life might lead to more varied and interesting dreams.

If you're looking into improving your imagination, you could try this exercise called image streaming:

http://www.winwenger.com/imstream.htm

I haven't tried it, but it's supposed to improve the imagination, and do a lot more on top.

And...last but not least, there's this tutorial in the tutorials section:

http://www.dreamviews.com/forum/viewtopic.php?t=11037

It's meant for increasing dream realism, but a more vivd and realistic dream could be a more interesting dream, so parts of it are definitely worth a try.