How can I display different sized designs in Adobe Portfolio?

[Sampxi]

This has been a continuous struggle of mine and I wanted to see if anyone in the community knows how to do this. I want to display various sized designs I've done similar to this person portfolio (Image attached, This designer also uses Adobe Portfolio).

[Nancy OShea]

Is your screenshot of a PhotoGrid or cover images on a main Gallery page?

One option is to put a black border around smaller designs in Photoshop before bringing them into Portfolio.

[Sampxi]

In the screenshot, they're cover images. I'll also use that other method if there's no other way. 

To be more descriptive, the person's portfolio is http://b-r.work/