Hi,
What profile URL do you mean? Are you using some other plugin for user profiles?
Job Manager uses the built-in WordPress user system. We do have an option in the settings called Account Username
you can turn off to include a username field in the job submit form, I imagine that’d be used for user profile URLs for other plugins.
If you mean the profile picture, by default, that is served by Gravatar for WordPress users, based on their e-mail, and they can customize their profile picture there.