An app, whether a SaaS or mobile app, needs many images of different sizes for all different platforms:
- the iOS App and Google Play stores (icons in sizes X/X'/X''/..., screenshots, ...)
- your app's Facebook page (icon in size Y, cover, ...)
- its Twitter account (icon in size Z, cover)
- ad campaigns
- ...
What tool(s) do you use to manage (upload/resize/edit/version) them?