Arista EOS is very customisable, but if you want to customise the image you are going to deploy it can take a little work. The SWI EOS image (the part we care about anyway) is basically a squash-fs file system wrapped up as an uncompressed zip image (store).
To get at the interesting bits:
unzip EOS-4.14.6M.swiunsquashfs rootfs-i386.sqsh(as root)- Make any changes you want (add files, edit the python files, whatever)
- Delete the original rootfs-i386.sqsh, and then make a new one
mksquashfs  squashfs-root/ rootfs-i386.sqsh - Zip everything back up again:
zip -Z store EOS-4.14.6M_custom.swi boot0 initrd-i386 linux-i386 rootfs-i386.sqsh version
Of course it is worth noting that the this would violate the Arista license agreement:
Customer shall have no right and Customer specifically agrees not to:
…
(iii) decompile, decrypt, reverse engineer, disassemble or otherwise reduce the Software to human-readable form ..
