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.