I live in Brisbane, and have the exact same problem. Sanity usually sells a couple of Paramore posters, and other than that, eBay is the best bet.
Skinit.com
You can buy Paramore necklaces in their official webstore (http://store.paramore.net/) or sometimes at Hot Topic.
U can buy Adam Lambert posters at Walmart and I believe at Target!
you can buy them at justinbiebermusic.com. That is his official site
Band posters are available for purchase at nzgameshop. They have a wide selection of over 300 posters of a variety of bands. They have posters of Foo Fighters, Nirvana, The Beatles and many more.
You can buy them from the websites, Hot Topic and other music stores.
You can purchase Paramore Posters online at the Grind Store.
depends on where you live, what shops are next to you, for example, if you in sydney, australia, in New South Wales, there is Kmart has cheap posters for walls.
You can buy posters in lots of magazines online.
Skinit.com
Will buy 15
You can buy Paramore hoodies from the Fueled By Ramen webstore or at Hot Topic.
yes you can buy posters from eBay and search in Google.
You can buy they from eBay but if you want from a shop you visit i go to just music shops in the city or you can go to the official paramore site and buy it online.
Hot Topic
You can buy Paramore necklaces in their official webstore (http://store.paramore.net/) or sometimes at Hot Topic.
One can buy posters made by Athena Posters online on the official Athena website. A dedicated agent will be happy to help you find more information on their official website.