Yes, there are options to customize the form on the pMailer subscriptions settings page.
A smart form is a subscription form that blurs out a web page and is displayed over the web page content. The form can be quickly filled in and then is not displayed again. The smart form can be customised to only get displayed to a user on your website has been to X amount of pages. E.g. The smart form can be displayed to users who have visited 3 pages on your site.
The smart form can be styled by changing the style sheet named subscription_form.css found in pmailer-subscription/css in the plugins folder.