I don't know WHY I didn't drop in on this thread earlier!
I don't want to discourage Rainbowgardener, but the purple flowered bonsai in the link she mentioned looks like wisteria to me.... Growing and training a native wisteria in tree-form in the font yard is one of my NEW PROJECT! For this year. Once I have that going, I should have plenty of cuttings or air/ground layered wisteria to play with. Still, Lavender should make for an interesting bonsai, shouldn't it? I have one that is not in an ideal spot. Maybe I could dig it up.... It's next to a volunteer mulberry that is also in a wrong location and has been root pruned a couple of times already so it can be potted up this spring.
I'm thinking any woody trimmed perennial that has tendency to back bud easily and is not too difficult to grow in containers (outdoor winter hardy, or indoor culture) should work, shouldn't it? Smaller leaves and naturally shorter internodes are criterias, or any of my avocado treelets could be a candidate (I have plenty of citrus seedlings, and 3 poms that have been elevated to potential bonsai status). I WAS surprised to see that mango bonsai. Hot peppers have been added to the list of possibilities -- I always thought the woody stems looks interesting... But I'm not sure if they would be long-lived enough. I have plenty of overwintering peps now to consider.
I have all kinds of "weed" volunteer tree seedlings in the garden that I've been allowing to grow for potential bonsai material, and now I'm adding my invading nemesis the English ivy to my list. I was unable to keep up with uprooting the invasion from behind my back fence last season, so come spring, I should have some interesting candidates to choose from!