you’re just looking for something simple to test out
your technique, or something easy to emboss, I recommend
towels. Embossing on towels will add a really cool
embroidered effect, but still leave enough of the “nap”
of the towel to make it useful as, well, a towel.
Polar fleece and a few other piled fabrics work well
too. Some furry fabrics will work, but only if the fur
isn’t too long.