I did see the WIP pictures yes, you're not even close to being half-way done =P
A trellis might look pretty good.. I'm wondering how good it'd look if it was covered with flowers and vines though, might be fantastic, might look really out of place.. can't decide.

Though I don't see the problem of simply adding a roof to it.
You don't 'have' to make all your roofs with a 45 degree incline, you could use the 1" long triangle blocks to get a 22.5 degree incline.
Looks like it will fit, barely.. but still.