Hi Loretta, There are two portraits featured at http://www.tnportraits.org/site-index-artist.htmhttp://www.tnportraits.org/site-index-artist.htm or search National Society of Colonial Dames of Americaor Colonial Dames Portrait Project - Index by Artist Scroll down the Unknown list and you will find both Robert and Matilde Lusk portraits.
I am searching for Benjamin B. Lusk married to Eliza Gay. Would love to see them myself but I live in Australia. You will notice on the site that their place of residence was 7th and Union Sts. Nashville.
Best of luck - please let me know what happens? Kind regards Angela