I wanted to Jazz up this onesie a bit, so I decided to applique a flower on it. I used "Steam-a-seam 2" found at most fabric, and some craft stores, and I cut out a flower shape in some fabric (I could have put more effort into my flower shape) after I fused the fabric to one side of the interfacing, I cut out the shape and ironed it on to the onesie. I used my regular old zig-zag stitch, but I set the stitch length to 1.5 (I tried it at one, for a more embroidered look, but the thread got too thick to feed under the presser foot). I was able to manouver it around well enough using my regular foot, and keeping the feed dogs up, however, if you applique a designe with too many curves it may be easier to put your feed dogs down (or cover them with a piece of card-stock, but then you might have problems controlling your stitch length). I would also be useful to use a darning foot, but then you would have to use a straight stitch, since you would be free-handing it.
When I was done, I added a matching button to the middle