How can I customize this shop's design to look uniquely mine?

What size does each design need to be?

Look up other shops with great designs to get inspiration!

Find out dimensions of all the designed elements of shops. Avatar, profile image, backgrounds, etc. Come up with specific aesthetics for each site and stick to them.

RedBubble

User Image

Cover Image

2400px x 600px

JPG or PNG format

"The cover photos are a generous 2400px x 600px in size, but keep in mind when you view your profile on a mobile device the outermost area of the design is not in view. You might have also noticed that your avatar repositions itself to the middle of the screen. This is helpful as it makes the mobile viewing experience easier, but might require a little bit of adjustment so nothing important gets hidden from view."

https://blog.redbubble.com/2016/08/designing-eye-catching-cover-photos/

Zazzle

Banner

1140px x 315px

Logo

512px x 512px

Media Images

1080px x 1440px

Society6

Cover Image

1000px x 100

Avatar

Unknown - The image should be square but will be displayed as round.

Society 6