Laura,
I'm going through a similar thing right now. I've had a moderate amount of success with name bracelets and other jewelry, but I can't seem to get the ideas in my head onto the design board. Very frustrating. So, I made a decision this past week - I'm going to go through my huge bead stash and liquidate stuff, then I'm going to go through my years of magazines and pick out projects that highlight techniques that I need/want to learn and only buy new beads to complete those projects. I think that in my case, if I can hone my technical skills, the design aspects I so long to perfect will come naturally. In the interim, I am content creating things with the skills I have now and look forward to the day when my mental image and the finished piece are one and the same!