Don’t use Aweber to make a form pretty. Instead create a basic form with a transparent background. Use your website or landing page for all of your design needs. Here’s a short video that shows you exactly how to build a basic form within Aweber.
If you decide to start using Aweber, please consider buying through my affiliate link. As always, if you become a client of theirs (or already are a client of theirs) and have questions… let me know and I’ll do my best to help!