Please remember to download this mod first:

Animated Banner/Billboard [Add-On] 1.1

https://www.gta5-hub.com/maps/animated-banner-billboard-add-on

These are pics I use with this mod, I decided to share them here if you guys want.

To change the texture:

Use Openiv to edit ytd "lafa2k_animation.ytd" file.
mods\update\x64\dlcpacks\lafa2k_animated\dlc.rpf\x64\levels\gta5\lafa2k_animated\props.rpf\

Choose either of these to change your billboard. Just double click lafa2k_animation.ytd and simply replace it with the pic of your choosing.

Just in case you don't know the picture dimensions are 1536x2048. You can make your own.