The embroider trim I would expect on a fleece blanket would be the blanket stitch. Here's one site. [
primrosedesign.blogspot.com]
If you put blanket stitch into a search engine you will get lots of sites with more information.
However, your subject line said crochet trim. I would guess there would be a couple of ways to do this -- if you have a crochet hook with a fairly sharp head that will puncture your fleece blanket you could do a single crochet edging. If you don't have such a sharp head on your crochet hook, you could punch holes at regular intervals around the fleece and then do a single crochet or whatever other crochet edging you would like. You could also embroider the blanket stitch around the edge and then insert your crochet hook through the blanket stitch edging to add your crochet edging.