My advice is the best baby flannel you can buy. The cheaper flannel sheds alot. Keepssakes quilting has alot of wonderful baby flannels as well as connecting threads. Carol
Flannel works great for me, soft and easy to embroider on. I've also used nice cottons and then backed it with fleece. So soft and warm and cuddly. Don't forget winter is coming........
Good quality fabric. Don't put a lot of time and work into cheap poor quality fabric.
If he is very young, use lots of different textures. Babies love exploring. Otherwise, you use what you love and you will have a great time making it and be giving him something full of your love and personality.;)