There is a way to update the /sil command so that it works for neon signs.
I would love it if we could get this changed. I've tested it on private server and it works great!
Here is the thread to the original post: https://umod.org/community/sign-artist/28103-support-for-neon-signs?page=1
I'll even paste it here, so you can copy/paste it into the code:
["sign.neon.xl.animated"] = new ImageSize(256, 256),
["sign.neon.xl"] = new ImageSize(256, 256),
["sign.neon.125x215.animated"] = new ImageSize(128, 256),
["sign.neon.125x215"] = new ImageSize(128, 256),
["sign.neon.125x125"] = new ImageSize(128, 128),