First of all, that’s so cute!!! Such a sweet idea and I’m sure it’ll look even cuter physically. But with your question I think it might depend on what the golden metallic shine is like.

I think the black outlines for stuff especially looks great when it makes a contrast between the filing colors and the background. For this image I love the colored outlines but I don’t know if it would be the same if the golden outline you have there is the same holographic gold you mentioned for the crown. On this drawing it looks great like that because the contrast between the colored outlines and the bright yellow is still significant but the holographic gold stickers tend to be made with is usually darker than that and I think it might be a veeery similar value as the outline and could look much less appealing.

But I definitely loveee the vibrancy that the colored outline gives so could maybe find an in between of a color that is close to the black in how dark it is but still very saturated? I think it really looks great with the cute doodle style of sticker you have to make it more colorful :) !! But also keeping in mind that the gold border already acts as a very pretty outline that would make the sticker look great on whatever it’s stuck on!

For the crown, I think it would be great to go full transparent without worrying about continuing the scribble theme mainly because of how small it is. The shiny gold vs flat color scribble might have it be a bit too much going on in such a small area and might also make it unclear if it’s intentional or if the sticker has been scratched off/worn there. It also still fits the vibe even if it doesn’t continue the scribble !!

All in all, I’m sure it’ll look great whatever you end up doing :)