I second dunster that adding 30 degree triangles would turn the blocks into rectangles. Do something like add solid 60 degree triangles, sort of between blocks. You can piece your blocks in "strips" that way. The secondary design would be a star. I found this pic on flickr of how it would work (not mine):
https://www.flickr.com/photos/quilti...ss/6265900610/
Yes, AngelinaMaria, you're thinking of octagons.
I recently did something similar to what you're describing for this quilt, but yes, that was for octagonal blocks:
[ATTACH=CONFIG]469787[/ATTACH]