From your question it is not clear if the master and slave PI will be on your home network, or on a separated and dedicated one. In addition, it is not clear what you mean by "sending images to be displayed by slave RPis". How do you send those images (FTP, SCP, etc.)?
Milliways already provided an answer when you have everything on your home network. Each RPis has a unique MAC address which you can map on your router side to a specific and fixed IP address. So you can on your router set that the RPi1 which is connected on port 1 and has a certain MAC address (on your RPi connected to port 1 enter the following command
ip addr show eth0 the MAC address is the one given for label
link/ether) has a fix IP address (e.g. 192.168.0.101 if your LAN subnet is 192.168.0.1/24).
In addition to Milliways answer, if you want it on your LAN, but your router does not support matching a specific MAC to an IP, then you could deactivate the DHCP function on your router and install and configure a DHCP server on your master RPi. This is however not possible to describe in a "short" answer how to do it. But search on the internet for: "install DHCP server" with either Linux, Debian or Ubuntu (if you're using Raspbian).
If you want it separate, you just need:
- 1-9 Raspberry Pis (RPis)
- 1-9 RJ45 Ethernet cable (one per RPi)
- a hub or switch with at least as many ports as you want RPis
Now just set all your RPis with static IP address on a same subnet. You can use for example: 192.168.3.14 for the master RPi, and then 192.168.3.1 to 192.168.3.8 for RPi1 to RPi8. The netmask should be 255.255.255.0. You only need to set the netmask and IP address, you don't need to set-up a gateway (obviously as there are all on a dedicated and separated network).
I don't know how you want to send images to your slave RPis, but you could use
scp to copy image1 to 192.168.3.1, and image2 to 192.168.3.2.