I've transferred a new folder to the desktop which contains Amiga files which I've transferred over from my PC.
Whenever I open it, it defaults to the DOpus setting of a lister. I can display the icons using ViewAs, but how do I tell it to display the icons from the get-go? Other folders (such as AmiKit or Favourites) automatically open as icons. I've tried using Snapshot->Lister, Snapshot->Icons and Snapshot->All, both on the drop-down menu and from the DOpus menu at the top, but nothing changes.

My setup is AmiKit 11.8.2 running on a Raspberry Pi (Special Amiga 37 edition).

Hello, make sure the folder you are opening has .info icon file too. The information is saved to that file, including snapshots. If there is no .info file, the lister will open in its default mode - which is probably the name mode.

Actually, while in name mode, mark that folder and from the upper-right corner of the lister select «Add Icons» and the proper icon will be associated to that folder.

Thank you. That was the problem; it didn't have a .info file. Once I added one the problem went away.

Where can I see a whole bunch of icons so that I can use the CopyIcon tool to add or change to ones I like?

You can start here: https://aminet.net/package/pix/picon/kens_icons_v4

And continue here: https://aminet.net/package/pix/picon/GlowRevolution3

In fact, you can take any PNG image (the ideal image size is 48x48 or 64x64 pixels) and just rename it to anything.info and it will appear as icon in AmiKit automagically

Check the following tutorial videos to learn how to unpack the archive or how to replace the icons: https://youtube.com/playlist?list=PLxEnP5UUSCcREBN5C0aCC-zZ5H_gK4FTV

Hope it helps?
Jan