About Texture

Hi everyone i’d like to create 2D paper background.As below a picture you can see there are cloud and cartoon ground or 2D texture.These are FBX type files.Are they created by Maya,3Dmax ? i have draw a cloud texture from photoshop then i imported it into UE4 my texture’s background became black only clouds became white i have no i idea about this.My question is how could i create a cartoon 2D cloud like the picture ? i only want a white cloud background not other background.Does anyone knows about this?
i’m sorry for my confuse english.

i’m sorry what does it means ? i can’t see what can help me that one.would you more clarify for me ? please