There are many inspiring things that come to mind when talking about building an aviary. It is fun to think up a dream aviary, sometimes it might be possible, sometimes impossible given how much space you have or how much money you have to spend. The right aviary should not only make you happy, but should keep your birds happy, so you must always think about that among other things.
Some of the most inspiring aviaries to me are the large, nicely landscaped aviaries. The more the aviary feels less confining, the more I like it.
Aviary inspiration can come from aviaries that are not even for peafowl. Some of my favorite aviaries are those at Pinola Preserve, which mainly keeps waterfowl. Bellow is a link to their aviaries. Keep in mind as you look at the photos the detail put into each aviary like the rock work and waterfalls. http://www.pinola.net/Gallery.aspx
Something I want one day is a giant greenhouse aviary. Some inspiration for that is a video of a greenhouse aviary for parrots. It is overwhelming all the things you need for a greenhouse aviary but it would mean you could have tropical plants with your birds and have better luck with more tropical birds. http://youtu.be/FNHZVTS4_44
Also Project Perry has an African Grey aviary that contains a greenhouse type aviary. http://www.projectperry.com/the_grey_aviary.php
Texas Peafowl has some nice large, grassy aviaries. http://texaspeafowl.com/pens_ideas_equip.html
Zoos are also very inspirational. The website zoochat can give you lots of ideas with their large database of zoo photos from all over the world.
Finally bird forums are excelent for finding aviary designs and also starting a topic asking for aviary photos or how to build an aviary.
There are many things to think about when building an aviary, and I hope this helped inspire you and get you thinking on making an aviary that is nice for you and your birds.