If possible, tags should include at least one adjective and a noun that accurately describes your item. Take the tags you have and make your title from that. Your higher item searches will be the ones you want in both title and tag.
For example, "cactus illustration" isn't as popular as "cactus art". If you are low on room in your title, put cactus art in both and cactus illustration in just a tag. "Free hugs artwork" is a better tag than "free hugs", because it covers free hugs, free hugs artwork, and hugs artwork as well as all three words individually.