I did Walmart registry. Most big box stores (Walmart, target, k mart, etc) should offer a good neutral selection. Oh, what about babies r us?
I registered at target. I noticed most major things you will meet are gender friendly. Like car seats and strollers have neutral colors that can go either way. Even swings and such have neutral colors. I had a jungle safari theme and alot of stuff I got in greens and cream colors with yellows. Nothin was really distinctive on blue or pink. They also have alot of baby clothes with neutral colors as well. You can go online and search the baby stuff to check it out before you actually register to see of they have things you'd like.
I did a registry at target and Burlington coat factory. Both have good baby depots