I can think of no evergreen vines that will look good blasted by a zone 6 Winter while in full Sun.
Two vines, not evegreen, that look nice in Spring, Summer and Fall are boston ivy and Vitis cognitae. Boston ivy turns brilliant colors before Winter comes, and the second, the Glory Vine, is also famous for large brilliantly colored Fall leaves. Well grown, the leaves might be 10" or more across. Lots to clean up when they fall.

Thanks for the reply! Is the Glory Vine the same as Morning Glory Vine? Does that have flowers? I say the wall is in full sun, but it gets sun from about 10:00am until about 4:00pm or so.

Can try Pothos or an ivy like english ivy.. they will not be evergreen in your area though. Morning Glory is very invasive where I live (Central Fla Z-9) I would never plant it here but maybe someone in your area knows better. In the froums listed look for your state.. i.e. Florida gardening and post there- that way you'll get folks from your neck of the woods. The wall sounds wonderful ! karen

Jen,
In zone 6 Pothos will never make the winter. My suggestion is not an evergreen, boston ivy or virginia creeper are beautiful in the fall though. The only issue I'd have and it's a biggie for me. Wasps, yellow jackets, if you're allergic be careful. Yellow jackets will nest in stone walls if there are spaces for them to get in, and wasps love to nest in vines.
That said, I plant vines all over my fences and arbors, none are evergreen for me here in MA but I haven't looked for any that are. If you can trellis the wall clematis paniculata / autumn clematis would cover it. You could also put some of the older climbing roses, sombrueil and zepherine drouhin do well for me. But again they're work and have to be tied up.
Hope I was helpful and sorry about the wasp scare but better safe than sorry.
chaz

Vitis cognitae (Glory Vine) is a non-edible grape, grown only for the large leaves that turn spectacular colors in Fall. I do not have the spelling of the name correct, but when I google the names in, I am often asked ' Do you mean....
Glory Vine becomes a huge plant that would cover a great deal of a big wall.
Virginia creeper is related to Boston Ivy and both would look great, but it is such a weed on my property that I never suggest it to anyone. All three plants form up a tangled brown mass of stems for the Winter.