404 errors on wordpress image attachment pages HELP PLEASE

This may seem like a dumb question but:
It seems that google somehow indexed my logo,favicon a 3 other images as a mysite.com/attachment?id-xxx
I removed the logo/fav and the images and now I have in google the pages indexed but they return a 404 page not found..(because I've deleted them)
How to deal with this problem? Should I redirect them? How and where?
And how do I stop google from indexing these image attachment pages?They are usless

Any help please?

Show a valid 404 page and google will de-index it. That or redirect it to the homepage and G will just drop the page eventually.

You mean like a custom 404 page right? Doesn't this affect rankings?