baby quilts can be used through the toddler years if made a good size. i made 45" double sided flannel baby blankets for my friends and they used them for years. i think you should use any pattern that you want to make your baby quilt. colors and fabric patterns can play a key role in keeping it kid friendly but really today, quilters are using all colors/patterns to make baby quilts: browns, grays, blacks/whites; colors i normally would not have associated with baby quilt.
have fun with your quilt project and good luck. using some wonderfully busy prints (and good quality fabrics) will help to camouflage many spit up spots.
