Is their a mod that.
 

that will allow me to make a user field for images
like i want the user to enter the URL to the image in their profile field and have it display in their profile. (kind of like a second avatar).

The current ACP only gives me options for text fields and radio buttons.

Just tell the users to input a fully qualified url into the text field. Then just treat it as another profile field in your postbit only instead of spitting out the text from the field, use the field as the url in an image tag.

Good idea im going to look in to it

You could use the "Regular Expersion" check on it (located on the page where you add/edit the field). Be best to check on google for the code to input in that option,, something like "regex valid URL" would probably get you some results.

Something I found from a quick search:
Not to familiar with regular expressions myself but you could try that out and see what happens.