As I see it, a tea towel is a utility item and as such, can be more casual than an item made for show or competition. Embroidering as neatly as possible is good, but I wouldn't worry too much about the back side. I LOVE hand embroidery and have many items from my sister, who does a neat job, but no covering on the back. I always fold them with the finished side out and hang them that way, too. So, to me, it the back really doesn't matter.