I think this might work better with either more or less of a silhouette. The problem is that I am drawn to the red tops of the cacti, but there isn't enough detail there. I think in this case, I would prefer less of a silhouette, rather than more. Fill flash (if you are able to use a high enough shutter speed) might work. Otherwise I like the composition and background. I could see this as a country album cover, but probably not with the band name ; )
I think because the cacti take up so large a part of the frame that they don't indicate Diminutive and also take a lot away from the image. The sky is lovely with the sun behind the cacti but most of it is hidden. Because some of the detail is showing on the cacti it has made that part into a dark area if you were to darken it more it would become a silhouette instead of being somewhere in between.