A deep forest blue-green and a deep rose would be lovely as the key colors and not girly. Batiks is a great suggestion. You do need to know the colors - green is a big place! Once you figure a number of colors you want to use, then you can worry about patterns, modern or classic. I doubt you will find a geometric or a floral in just the combo you need (I went through that with teal and peach last fall and it was a total waste of time - you may need to find complementary prints with a joining color. I ended up using a lot of cream background.)
sounds like a wonderful project - Good luck!