Here's what I think. The D
-7 chord is what's called the "relative minor" to the G chord, so it fits. I sometimes play a D
-7 chord on the right hand, in root position (D, F, A, C) and a single G note in the left. This is a very effective way to resolve back to the root key, which I assume is C in your case.
Using this technique, the accompaniment instruments will also play a single G note all in unison, which may sound wrong but in fact, you often hear this in full orchestras. It gives the listener a break from all the little nuances of the other instruments. Listeners need that break once in a while. Don't underestimate the effect of playing the minor two in the right hand and the fifth in the left. It's very powerful and used by a lot of pro players
!
One more tip: For extra effect in resolving to C, instead of playing the D
-7 chord on the right, try either a D diminished (D, F, G#, B) or Fm
major7,flat 5, which is F, G#, B, E. At first, it appears to conflict with the rules of theory because you have a G and G# in the same chord, however, in Jazz, you can get away with that when those two conflicting notes are spread far enough apart.