Generally, I've found simplicity is best. I think that I have a tendency to take things too far. One example is pretty much any art project that I did in school (before I became a lazy highschool/college student). I'd work on it forever, keep adding things, until it just got messy. I've been learning that I need to take good ol' Tim's advice and bring and editing eye to everything I do. That said... It's still fun to embellish a little every once in a while.
Like with onesies. I think that people can take embellishing onesies to a crazy level. Just search "onesie" on etsy and you'll see what I mean. Applique, stenciling, stitching, ruffled bums are all great, but individually, not all on ONE onesie. (well maybe except for the ruffle bums, which frankly, I just don't understand. I guess people figure "hey! My baby's bottom is so huge with this diaper I might as well do something to it!")
I think that freezer paper stenciling has a lot of potential to be fun, inexpensive, and still relatively simple at the same time. I'm still not sure if anything can be cuter than plain solid colored onesies on babies - but sheesh, you can't do that all the time right? right. Life needs variety. Now that I've talked myself in circles, here are some cute freezer paper stenciling ideas that I've marked for future reference: (and here's a site with some great tutorials on freezer paper stenciling)
I think this one is great - simple and cute. I really like the idea of white on a colored shirt.
Funny, and a little ridiculous. I'd probably be embarrassed to take my baby out in this just because I'd feel too nerdy. I like the idea someone had of using it as a halloween costume.
And lastly, I seriously love this one. Pacifist. Genius.