ADVICE NEEDED: Building a chicken run that doesn't look - well, trashy.

This is my chicken run. It is covered in plastic for the winter but when not covered it looks pretty nice

If I ever get around to painting it white it will look even nicer, lol.

I think just be sure you fencing has adequate support.  Use lumber, not T Posts, and attach it well.  There is no reason there should be any sagging with adequate support.  I used 4 X 4s, sunk about 2 feet deep and spaced about 8 ft apart.  I used 2" X 4" utility fencing all around, with hardware cloth on bottom and as an apron.  I was a healthy sized investment, but I am way past worrying about anything 'falling apart'.

The idea that any fencing to keep in over 10 birds will definitely sag is absurd.  It's not the size of the run, it's the quality of the build and how much you are willing to invest in it.  My run is appx 16' X 20'.  Probably cost me about $500 (More than building my coop even) but it's a one time investment and was well worth it.  It could have been done more cheaply if I had the ability to get stuff off craigslist and were willing to wait until things became available there.  Instead I bought everything new.  Since then, I've seen lots of things on CL I could have used if I had the ability to pick them up.

Good luck!

This is mine, this spring I will be continuing the Ondura roofing to cover the rest of the roof , right now it's 1/2 mesh, but I'm finding I want the whole thing covered:)

I just wanted to add that a proper fencing job will not sag.  Dig at least 2 foot deep holes for fence posts and space them close enough together with some cross-bars for added support.  Spacing them closer together will also allow you to stretch the fencing material (hardware cloth, chicken wire, whatever tickles your pickle) to keep it from sagging.  Loose, improperly secured fencing sags.  Nice, tight, secure fencing does not.

I had my contractor build this run for me. He sunk lodge poles 2 feet into the ground and cemented them. Then Hardware cloth was placed at the bottom with an apron extending 18 inches out on the ground and 18 inches up the sides. Above that was 2x4 non-climb horse fence attached to the hardware cloth with hog rings. We eventually divided the run into two and built a second coop. He also built sturdy gates. The entire run was covered with flight netting as well. Nothing penetrated this fortress in the two years we lived there. Unfortunately raccoons got in during the night by coming down the tree and got my turkeys that refused to go inside at night. They were one day away from being moved to the new house. The cable around the top was for holding the flight netting up. We draped it down the sides and attached it to the horse fence with zip ties.

The new house has five coops with similar fencing around the perimeter, except the horse fence is 6 feet tall. Between the runs we used vinyl coated chicken wire, also 6 feet tall. The entire thing is covered by one piece of flight netting. Hasn't been trimmed yet in the pictures.

I don't think my runs look too bad. We are very careful about junking the place up. We are in the process of painting the coops to match the house.