hmm i just entered Time Machine within iPhoto and i dont think you can?! i tried selecting a photo and pressing both delete keys and command+delete and nothing happened. theres also no trash in the iPhoto Time Machine UI?
I needed to do a similar thing. I have been going nuts ripping my DVDs for my ATV and as a result of letting my iMac run all night doing encodes time machine had been backing up those files. Next thing I no, I only have 130 gigs left on a 500 gig drive. Well, I came across this article: