I've been given a solo over Bminor7 to Bb7. I've found a few phrases I like within the chords, and especially like working with the D (3rd of both chords). My question is how would I go about getting away from just using the chord tones. It sounds pretty lame when I'm stuck going to the root of each chord on the 1 every bar. I know this is vague and open to creativity, but I'd just like to know how you guys would theoretically approach this progression. Any "safety scales/modes" you would use, other chords you would imply? Thanks for any input.

one approach might be to look at the Bb7 as a sub for E7, and play as if it were a straight ii7-V7 (Bm7-E7).

without the song for context it's hard to get specific

You could state something using the B blues scale on B-7 and then repeat it or answer it using Bb blues scale over Bb7. Might be worth a shot.

Trying an F#minor idea over the Bminor7 (working off the "5" of the chord), then repeat it or answer it using a Fdorian minor idea over the Bb7 (also working off the "5"), could be fruitful if handled tactfully.

I would really just try to play what I hear (easier said that done, right!), but those are some things you could try. If you have band in a box, you could plug the two chords in and work up ideas by yourself.