Picard is present in the Canonical Snapcraft repository and Microsoft store. Those stores provide the ability to upload larger banners that are used to advertise the application in the store. See:

https://snapcraft.io/picard
https://www.microsoft.com/store/apps/9NJ9Q3JR29L2

Design and create nice looking banners in the appropriate sizes to replace the current ad-hoc images.

These images are needed:

Ubuntu Snapcraft
Min resolution: 720 x 240 pixels
For best results on the store we recommend a resolution of 1920 x 640 pixels or greater
Max resolution: 4320 x 1440 pixels
Aspect ratio: 3:1
File size limit: 2MB

Current: https://dashboard.snapcraft.io/site_media/appmedia/2020/12/picard-banner-snap-store5.png

Microsoft Store

2:3 Poster art (720 x 1080 or 1440 x 2160 pixels)

(currently not used)

1:1 box art (1080 x 1080 or 2160 x 2160 pixels)

Current: https://partner.microsoft.com/de-de/dashboard/listings/FileV2?productId=9NJ9Q3JR29L2&storeListingId=1152922700003575600&submissionId=1152921505694506014&listingAssetId=1152922700003575664&targetWidth=350&useResizedImage=true

See https://docs.microsoft.com/en-us/windows/uwp/publish/app-screenshots-and-images#store-logos

Social media preview

This is set on the Github pages, but could also be set on the Picard website. Social media sites, blogging tools and forum software (e.g. also Discourse) might show this when linking to the resources.

Github recommends "Images should be at least 640×320px (1280×640px for best display)".

Current: https://repository-images.githubusercontent.com/2218679/ac0f7600-1748-11ea-938b-82d4c3d57621