Currently the world loading screen of BedrockIfy uses a custom texture, which means it looks quite out of place with resourcepacks applied. Instead of asking resource packs to add support though, how about using existing vanilla textures instead?
More specifically:

• the window could be textured by the advancements screen, from /assets/minecraft/textures/gui/advancements/window.png
• the loading bar could be textured by the default XP bar, from /assets/minecraft/textures/gui/icons.png

Thanks for the suggestion! I'll take a look and see how can I improve it