There is a reason the texture pack is not up for download. If they made it downloadable, all of their custom textures would be up for everyone. Basically other servers could steal all of their hard work. The texture pack includes all of the models of each and every pokemon (hundreds upon hundreds of hours custom modeling each and every pokemon), all of the pokeballs, items, animations, pokestops, backpacks, hats. Literally everything you see on the server. So while it may be annoying to have to download it every time you log in, it is VERY understandable as to why it is not public.
As much as I want this to happen. Since today I spent 30 minutes trying to get Pokeworld resource pack to load. I gave up and left the server. I don't see this happening at all But i think I saw away to go into the server resource pack folder. Then through there you can some how transfer the texture pack to the resource pack folder. But not sure if you still can do this or not. My suggestion is to make the resource pack for Pokeworld easier to load. Like skyblock's or murder game mode resource pack does.
Best way I've learned how to get it to properly load is to just continually to delete the pack, relog and redownload until it works. If it fails to fully download, it corrupts and has to be deleted. Sometimes it takes me quite a few tries to get it to work.
I don't really want nor expect them to ever release the resource pack. But this does bring up a scary question. What happens as the resource pack continues to grow in size? Each new generation would considerably increase the size. As do new decorations, items, etc. There will come a point when its too big to load the way its done now.
Doubtful as they are just pictures and images. The file size will always be relatively small regardless of how much is added. However, the more they add, the longer it will take to download. But even so, I don't see it as an issue. Can you kill parts of your banner pls? xD it is obnoxiously large lol.
Firstly shooting your picture is too big like Ordaine said . Secondly the file size isn't that big it's just minecraft file download speed is slow