Beej

In WordPress, attachments default to having their own pages. Sometimes, 
this is not desirable, as in search engine results. Use this small plugin to 
redirect your attachment pages to the post parent using a 301 redirect 
(post parents are also searched for by post name). If an attachment parent post 
cannot be found, it redirects to your blog home page with a 302 redirect.

Attachment Page Redirect X

Redirect attachment pages to their parent page (301), when possible, otherwise to the blog home page (302).

Storm Consultancy

Perform a 301 redirect from an uppercase URL to the lowercase version for all non-admin, non-file URLs

Force Lowercase URLs

Perform a 301 redirect from an uppercase URL to the lowercase version for all non-admin, non-file URLs

Attachment Page Redirect X vs Force Lowercase URLs