Watch the Country Waltz online guitar lesson by Vicki Genfan from 30 Strumming Patterns You MUST Know
Here's a great 3/4 or 6/8 pattern for any kind of waltz-ballad. I'm playing G-Cadd9.
I'm picking out the bass notes and alternating strings. Try playing it with different chords and see if you can find bass notes that are interesting and provide some nice harmonic movement.
This pattern works well at many tempos - try it!