To get your images back, you may be able to contact your web host to see if they have a backup. Usually they will restore the backup for a nominal fee.
If they aren't able to do this, do you have the images on your computer? If so, you could first replace the deleted folder by going to Dashboard > Updates and re-installing WordPress by clicking 'Re-install Now.'
Then you could re-upload all of your images and attach them to the appropriate posts/pages.
This would be more of a last resort, though, just because of the amount of work involved so check with your web host first.