Dominant pedals are the most common type and a range of consonant and dissonant chords can be played over them. Most of these chords work best when they resolve each time onto some sort of V chord before going onto another one.
Diatonic / consonant
These chords can be used freely (they are not dissonant so are not technically pedal harmonies).
Some of these are seriously dissonant and need careful resolution. Each chord individually needs to resolve back to the original chord V (in this case G) before moving to another one so vii7 of V – V etc.
These are the main diatonic and chromatic passing notes that work in thirds or sixths. They can also work as auxiliaries.