RetroPie / Pimiga / Amikit XE / KickOS / Amiberry
Introduction
Different Pi images are popular within the Raspberry Pi community to quickly allow you to test out different OS, of course Amiga fans have started making Amiga themed / focus images that allow you to boot straight into an Amiga emulated setup and development of this has only improved as Pi systems have become more powerful and emulation support improve. Below are some of the main ones.
It should go without saying that you should only download games/software you own or legally allowed to be shared.
Retro Pie
One of the more popular images for pi's has been Retro Pie, its main purpose is to run emulated computer games of the past, including Amiga's, you can learn how to set this up and run it here, https://retropie.org.uk/docs/Amiga/
However there also pre setup one available too, not too sure on the legality of these images, but it does help end users have a quick setup, these also usually have nice art work and video intros for each game to make it easy to quickly find a game your after,
Tomato Amiga Retro Pie 32Gb is a popular one, designed for Pi3, click here for more
Ransom Ultimate Amiga for Raspberry Pie 3 v2.0 a 128Gb collection (for pi3) click here
DZ Commodore 64 & Amiga Only Raspberry Pi 3 B+ Image 16Gb (for pi3) click here
Hyperspin is also a popular image / system that not just focus on Amiga but on various system, with really nice presentation of front end user interfaces, usually full graphics and video gameplay of Amiga footage is used, you can see what them system look like here
Most people use this kind of build just for the Games and so I would recommend another build for full AmigaOS experience.

Pimiga
This is becoming a popular build for its large pre-setup system (not too sure on the legality of all this, but it is provided as non functional) you will need Amiga Roms for the system to work which is easy to setup. Then you are taken in a highly customized AmigaOS3.1 GPU setup with almost every game and software you can think of for Amiga, all pre-setup and ready to go. Designed for Pi4 & Pi400 systems only.
https://odd.blog/2020/09/24/pimiga-amiga-on-the-pi/
https://www.youtube.com/watch?v=KLJk8fTjQLw - Pimiga 2.0 video

Amikit XE
Already one of the best distributed pre-configure Amiga setup you can get for the PC, its making the jump to Pi, with features like Rabbit Hole as well allowing you to still have access to linux apps from within the Amiga emulated setup making them feel part of the OS meaning this is a true solution to dumping your PC for Amiga!
https://www.youtube.com/watch?v=ojjnLtjpBv4 - My video on the set up

KickOS
KickPi-OS is aimed at Amiga friends who want to revive the Amiga experience on a Raspberry Pi. The focus of KickPi-OS is easy handling and Workbench like "Look and feel" 🙂 installed and pre-configured on Amiberry,Linux Desktop, Retropie system.
https://www.facebook.com/
https://www.youtube.com/watch?
https://onedrive.live.com/?
https://www.youtube.com/watch?v=lK6f0vYhqa0 - older video

Amiberry
Most of the above wouldn't be possible was it not for UAE4ARM and Amiberry, which is a optimized version for Pi boards, the clues in the name really.
https://blitterstudio.com/amiberry/
Aros ARM - raspi-armhf-system
The native version of Aros for ARMv6 based Raspberry Pi computers. Contains all files needed to boot from a FAT formatted sd-card.
Pi Amiga Case
Pi boards are not that interesting to look at on your desk, what we all need is Amiga Themed Cases!!! Lucky for us Amiga fans their are a number of cases that are designed for the Amiga fans that you can buy or 3d print out yourself.
Retro Amiga 3D Printed Case - A500 designed case - https://www.etsy.com/amiga-retro-raspberry-pi-case
Classic Amiga Mini Case - Simple square version of a Amiga case https://www.ami64.com/product-page/classic-amiga-styled-raspberry-pi-case
Amiga 3000 Case - 3d Print your own mini Amiga 3000 case - https://www.youtube.com/watch?v=zv4zgpyBvr0
Checkmake A1500 Mini - Not only can you buy the case but you can have a premade setup with Pi4 & Amikit XE - https://www.checkmate1500plus.com/
A1200 New Cases - Supports place to put a Pi in! - https://www.a1200.net/
For more details on Pi hardware, vist Amiga pi Hardware page here
Futher Reading
https://retropie.org.uk/docs/Amiga/ - Retro Pie Docs
https://www.youtube.com/watch?v=9WRP0_fjquc - Guide to Amiga Emulation on Pie
For finding games:
- WHDownLoad – a repository of pre-installed WHDLoad games
- Turran’s WHDLoad Pack Downloader — this is a tool for downloading pre-installed WHDLoad games from the English Amiga Board’s FTP site. These often have more up-to-date slave files than the games available on the WHDownLoad.
- WHDLoad – official WHDLoad site, which also contains a repository of game installers (note that these are not pre-installed like above and you need the ADFs to install the game to your hard drive)
- Vintage Is The New Old (formerly Commodore is Awesome) – general retrogaming resource with a heavy focus on all things Commodore; includes some downloadable Amiga games
- Amiga TOSEC – a free downloadable 37GB (yes 37GB!!!) archive containing multiple sources of nearly every Amiga game, demo, programme and cover disk ever made (excludes Workbench disks and Kickstart ROMs)
- EmuParadise – huge catalogue of classic games, including downloadable Amiga ADFs and CD32 disk images
- Planet Emulation – a French site hosting a large number of Amiga games