Hello there 
This time I am here to help you out a little with the artistic side of writing an episode story. Having good backgrounds and overlays can give your story that boost it needs and turn it into an amazing story, the visual aspect is more important than one might think.
Backgrounds
There are multiple possibilities when it comes to backgrounds and I would like to discuss them 1 by 1.
Using the original episode backgrounds (if not edited)
Episode created some amazing backgrounds, it really isn’t a bad thing to actually use them cause they are there for a reason, however, I personally think it is great to use these backgrounds as a base and add certain elements to make them more personal. For example editing in pictures of your characters, adding clothes your character wore or changing colors of furniture. I know not everyone is able to make these changes themselves, but in the #request-services:art-commissions section you can either find art shops who can do it or make a thread to ask for the edit to be done.
Using real pictures from for example pixabay
There are multiple data banks filled with free to use pictures, personally I would be careful with using these because the style is very different from the characters which can give the reader a weird feeling when reading your story, but you might be able to find hidden gems in these kind of data banks. Here is a website showing multiple of these websites:
https://buffer.com/library/free-images/
Other options
You can always draw a background yourself, or request others to do it for you. Also there are some people who have drives filled with backgrounds specifically for episode and in that style, for example episode life. Please credit the artist in this case! Lastly, episode also has multiple background sharing threads which might be worth it to check out 
Overlays
For overlays lots of what I’ve told works as well. I just want to specify some things
Websites for overlays
This is a very good one:
But there are many more, if you can’t find the right overlay you can always google: _______ PNG, and enough free to use websites will pop up!
Turning a part of a background into an overlay
This is not that hard, in for example ibis paint you have a selection layer and multiple tools that are useful for it, but it takes some practice so if you fail to do it there are more than enough people including me who can help you out with this!