We're after two things here: a badge and a certificate.
Badge: The goal is for the participant to place this badge in the sidebar of their blog. Therefore, a size of 250 x 250 px might work well (no larger) but other smaller sizes will be considered. Ideally I'd like this to be scalable and still legible if we convert it to a smaller size. I'm not going to give much detail on the design other than to say it should be vibrant and fun.
We do have a logo that we've used, which I've attached, but please apply some of your own creativity.
There should also be a space for the author of the course to add their signature.
Whilst the course that these items represent have been created from within the SitePoint brand, you don't necessarily need to take aesthetic inspiration from the SitePoint colors/logo/theme (in fact we'd rather you didn't take inspiration from the logo—large shapes of dark blue or orange rarely work well). These designs need to stand up and be identifiable in their own right.