You might consider making the language in your alt text actionable, such as "Click here to download the ultimate content creation kit." Actionable alt text will essentially turn every linked image into another CTA. So, even if someone doesn't see the snazzy GIF of my latest offer (or if they hover their mouse over an image that does show up), the alt text will beckon them to click.
Drip offers a very small forever free plan, along with a two-week free trial for the Basic and Pro membership levels. If you choose to continue service after those two weeks, then your card will be charged. There is a 30-day refund window from when you start your service, but it’s up to the discretion of Drip whether you will receive a full refund.