I have hundreds of pics that I've taken with my camera or saved to my phone from IE. I want to clean them up by deleting pics I no longer want, but I don't want to delete all pics. Is there some Explorer-like UI that I can use or anything else that doesn't involve deleting each pic one by one? It takes about 5 seconds to delete pic from the time you tap the thumbnail, hold, click delete from the context menu, and then move on to the next pic. There's no way I want to do this with a few hundreds pics.
There is no native built in solution but you have three other options:
Download Zune on to your PC and use it to delete/modify a bunch of files on your phone's file system.
Add a feature suggestion on the Windows Phone User Voice website or upvote one of these existing suggestions: "DELETE MULTIPLE PHOTOS" and/or "File Manager for Windows Phone". If you stay on Windows Phone 7, it is unlikely that you will see this feature added but if you switch over to Windows Phone 8 in the future, this would be a real possibility.
You could connect your phone to your PC and use Windows Explorer to view the photos and delete them. You do not need Zune to do this as the phone will show up in Windows Explorer as USB storage device.