Consider making a bunch more twister blocks? You could add scrappy twister bits even with the white deal you've got going there-- it would end up feeling like an internal frame effect and could look kind of cool.
It's very much a matter of taste, but I personally don't like wide borders or multiple borders on a smaller quilt -- to me they look out of proportion and detract from the design. If you're not inclined to make it bigger with more twisters, I'd seriously consider just accepting that this is a wall or table topper size and embracing it as is.