I share how to make glowing BG in Blender and how to composite 2D animation with this 🐆
This way is as same as I used in Elita & Renata animation


Delete all and put Plane from Mesh
Rotate R→X→90°, R→Z→90°

Adjust scale as same as the movie or image what you use

Open Shading then make new Nodes
Delete Principled BSDF. Plug Nodes in order like this

Push Open and import the movie or images into Blender
Adjust total frame number

Add another Plane and resize this to bigger than cel
Move this to back a little

Open Shading then make new Nodes
Delete Principled BSDF. Plug Nodes to Emission
Open Render property and check Bloom button

You cam adjust bloom details here

Set camera

After that, just do rendering
