To filter which contacts are shown in the People hub: In the People hub, tap the three dots at the bottom. Select "settings". Tap the button "filter my contact list". You get a screen with "show contacts from" and checkboxes for your various accounts (google, outlook, twitter, facebook, linkedin). Adjust as needed.
To see communication history for a single contact: Tap on that contact either in the People hub, or a tile you have pinned to your Start screen. Swipe over until you get to the History pivot. This shows all communication history with that person (phone calls, texts, emails, and possibly Facebook... not sure). It's pretty cool.
Pictures: To change what gets displayed on the tile itself, go into Pictures, tap the three dots, and select "choose background". This will let you pick a photo to use for the background in the Pictures hub as well as display on the tile. The Pictures hub will show you albums that you have on your phone, SkyDrive, Facebook, etc. If you don't want something to show there, remove it from the source. Or, on SkyDrive, you an always set the folder type to "Documents" instead of "Pictures" via skydrive.com.