How can I add a bonus to my Sprunki mod?

I'm working on a sprunki mod and it occurred to me to add the Ultimate Melody 5 and make Tunner part of the Voices (because the whistle is like a voice but sounds like an instrument, it sounds crazy) and I started working but I ran into a problem is that every time I put the character icon to a post it doesn't load (I think it's because there is a list called characters and there are all the orders of the sprunkis, the Ultimate Melody 5 is number 21) and that I put a lot of patience searching sprite by sprite for some code to add I don't know what so that the list has a length of 21 (because my sprunki which by the way is mard is number 21) could you help me? (sorry if it was not fully understood)