Ask HN: How to make all your marketing images for the app store?

I'm finishing and releasing my first mobile app. Right now, my biggest issue has been that Google requires me to have 8 photos with exact dimensions.

As a one person dev, what resources should I look at that'll help me make modern splash images?

I know what I'm asking sounds vague, but I've seen a lot of mobile apps have very similar images and marketing videos, so I was wondering if there was a good service/app that I didn't know about.

Deploying my app has taken even longer than making it!