I'd like to add a "Featured" symbol near the post meta...how would I go about doing that?

Against all or just some?

Some, depending on what entry it is.

give your featured articles the tag @featured and add the following code to the Entry Metadata where you want the graphic to appear (replace image name etc with your own).

Can I a href it and add a link to the thing as well?

yes, you can add anything you like between the EntryIfTagged tags and it will only be added if the Tag matches. I use it to insert additional JavaScript and widgets based on the tags users give the entries.

I can't embed a link into the .png image... exactly what is the code needed to add a link inside it?

Same code as any other image link