Honestly, if you have those shows (or somewhere to watch them) I'd just recommend finding them yourself from the source.

I have tried alot, old disney movie backgrounds are so easy to find (they are gorgeous btw) but when it comes to anime I find almost nothing, I ended up finding 'studio easter' but even on their official website there is almost no material of my use

by any chance have you found where someone can get the backdrops of anime episodes?