First of all I'd find out if she has a theme for the nursery. Doesn't mean you have to follow it, but it does give you a place to start. I tend to let my fabrics guide me in my choice of pattern (not that I actually follow a pattern anyway, LOL)
For either boy or girl, primary colors, alphabet/numbers, are always a safe choice. Winnie the Pooh can also be for either boy or girl.
For a boy, there are some really cute jungle animals fabrics that I've seen. These are in the greens/browns colorway. Or you can always do something with bandanas and denims. I did a red, white and black quilt for DGS.
For a girl, fairies/tinkerbell work really well. I just did one that was all pinks with adorable ballerina fairies and another one with primarily tinkerbell along with some other fairies that is aqua, purple, and lime green that still needs to be sandwiched and quilted.
Texture friendly can be really nice too. . .satin, minkie, corduroy, velvet, flannel, etc.
I'm sure that whatever you do will be wonderful!