SMom, are you looking for tall or short plants? Also, perrenials or annuals?
Lambs Ears are nice, but they take over. They produce a tall purple flower.
How about Impatiens?
Or hosta?
There are a million varieties to choose from, lol..Toni

I think you can't go wrong with hosta or impatiens.....and there are some heuchera (coral bells) that I've seen in these situations. The purple/red leafed heuchera add a nice contrast to the hosta plants. You can find a lot of the purple/red leafed heuchera at the Home Depots/Lowes. I've seen "Purple Palace" just to mention one.

Everybody and their brother, and their brother's dog, and their brother's dog's cousin, and their brother's dog's cousin's lawyer, and...

plant's hostas under their trees. Do something different!

I've got two neighbors who've done this to thier trees. The first planted a large variety of peonies around her tree then used large grey stone as a border. I loved the look of it. Very classy.The other did about the same thing, but used large, leafy plants that were non-flowering.

I would recommend a varity of hardy geraniums too since you get so much sun.
Though I love hostas, I wouldn't recommend them for you since you get more sun than most hostas like.

Heather

I have heuchera purple and mums under mine it is a nice combo.