So ive recently upgraded from iphone 4 to the galaxy s3. Just lookng for some site suggestions. Loking for ring tones and wall paper and anything cool. Thanks for any help.
xda-developers is awesome but maybe since you just got Android its not the best place. Most of the stuff there is to do with rooting/flashing phones.
To make custom ringtones or notifications just put any MP3 file onto your phone's SD card or internal memory under "\Ringtones" or "\Notifications" folders depending on which you want it to be. Ringtones is for your contacts calling you while Notifications is for Messages, Twitter etc. (most apps allow you to set a specific tone for their notification rather than all sharing the same).
Wallpaper: Google is your friend. Find a high enough res image and download it to your phone. Set that as the wallpaper and voila. There's not specific sites to provide Android wallpapers because all phones have a different screen res.
Recommended Apps: Dolphin HD (great browser though I'm currently not using it since Pinch Zoom is broken on Jellybean), Nova Launcher (if you don't like touchwiz. Stock ICS/JB launcher with extra customising), Flipboard (very pretty news app. Has several categories to get you started), Google Goggles (mainly use this as a QR code reader. Reads info from pictures and Googles them)