If you want to make all the images in your bucket world readable,
go to Bucket -> Properties -> Add Bucket Policy
and paste the following: (Remember to change the bucket name!)
{ "Version": "2008-10-17", "Id": "", "Statement": [ { "Sid": "AddPerm", "Effect": "Allow", "Principal": { "AWS": "*" }, "Action": "s3:GetObject", "Resource": "arn:aws:s3:::YourBucketName/*" } ] }