If you can get a theme builder to do it for you then yes. Or just download a theme and whatever landscape background comes with the theme will be the one you see
I you buy Patternlock application it allows you to pick a portrait pic and a landscape pic when Patternlock is activated. I use two different wallpapers. They have updated this app on a regular basis sometimes 2-3 times in one day, check it out. Great value for the money, when I bought it it was .99 cents but I think it is only a couple bucks regular price.