Depends on what the issue is. A few solutions that I've used for different circumstances:
Branches can be trimmed if they don't fit well--sometimes simply trimming one section to allow you to place it in a different orientation helps. Or you can cut it apart and remount the branches on a piece of slate or zip tie them together (hidden by the substrate) and plant heavily around the base to create a more interesting form.
As already suggested, adding plants strategically can help hide bare spots--especially on branches with long straight areas.
If it's the color of the branches that's a problem, be aware that manzanita branches will darken dramatically over time--mine were a ghostly silvery gray on arrival, but within two months were a deep rich brown.
If you got something like malaysian drift wood and it showed up in a big block of blah, you can take take power (or hand) tools to it and shape it. My first piece of malaysian drift wood was a featureless triangular lump--but when I took an axe to it and ripped it in two a strongly curved grain line was revealed and I ended up with two really lovely pieces. Sometimes just cutting one end flat to allow it to sit differently reveals a better form--I've done that a number of times with less than stellar mopani, along with drilling out knot holes, carving deeper into the wood to create stronger curves and cutting grooves to accentuate the grain and give it a bit more character.
Or put it aside to be traded, sold or used in a different tank and order more (this time preferably from a source that shows you pictures). Most folks I know who have wood of any sort in their tanks have a stash somewhere of bits and bobs that didn't work this time, but might on their next set up.