If I sewed fabric details onto a leotard, would it still look nice?

instead of sewing it on u can use a product called wonder under. it allows u to iron things on

I have no idea what you are trying to make but likely you will get holes and runs in the leotard if in fact make from nylon. . Do as our Farmer friend said plus be sure to use a ball point needle on your sewing machine. This type of needle is especially made for sewing knits. It will help keep the leotard from getting snags and holes. . What you are attempting to do is not something that I would take on as an experienced seamstress. You cannot applique fabric to a knit fabric that needs to stretch to fit your body. Unless you are only tacking as was already suggested to you, it will be an ugly homemade mess. . Good luck!

Please allow me to add some artistic ideas. If you use a double-knit (it will wretch sideways AND up and down) fabric, you will have better luck. Also, consider using lace fabric, which comes in many different colors, and cut out sections of the lace such as flowers or certain parts of the design, and pin them on the leotard WHILE YOU HAVE IT ON (because of the stretch of the leotard). You could glue on beads or see them on but don't pull the thread too tight or it will teat a hole in the leotard. But befrie you do anything, put the leotard ON and use WHITE CHALK for you and a friend to help draw out a basic design on your leotard so you will have a perfect idea of where you want things to go. Draw ideas on a piece of paper, out it on, and draw where you want to place things, and then maybe even pin your pieces of very lightweight or see through lace STRETCH fabric on there (if you still want to do this) or use the chalk marks to decide where beads will go. What would I do? I would do it all. Stretch lightweight fabric, cut out designs of lace, AND well placed beads.