Thanks for the swift reply guys.
I have several marketing images showing the face in a watch frame, with supporting text (all 16:9) and I had one screenshot in 1:1 aspect ratio which was a .png file (as provided by WFS).
I got exactly the same message as SGWatchDesign did when I submitted this, which, to be fair, only refers to WearOS screenshots, so I’ve converted the screenshot to a .jpg now and we’ll see what happens!
I’ve found before that the Wear OS status does not change when you submit a new version. It stays as “Rejected” while they do another review. One would expect that it would change to ‘in review’, but it doesn’t. In a few days you should get an email from Google with the result of their next review.
I’ve just changed the screenshot though and not bothered uploading a new version. Let’s compare notes in a few days!
I’ve uploaded all my screenshots as JPEG, always … But it was rejected
I am uploading watchfaces from a Month now always had this HR issue but today i got rejection on this
"
Your Wear OS screenshots include transparent backgrounds or masking.
"
Which is weird as I always take SS from WFS and submit them on Playstore they never gave me this error. What they mean by transparent background ? should i make background white now 
if someone knows do let me know as well.
Just make sure you are making your images 16:9 so 3840x2160 or 1920x1080 or 1024x786 JPG or PNG does not make any difference.
I had a case that the name of the app didn’t suit them, though they didn’t give a reason. Then I got an info in e-mail to change only the title without changing the version. When this is not in response from them, I change revision and add again.
My all images are of 1920*1080 Google Review team is so weird
It has now been approved. I have only a product image with GW4 and otherwise only screenshots from the WFS as JePG. No idea what Google thinks. Now it looks like a cheap product without good advertising / description
Have you checked the condition of wear OS?
Still rejected or active? It looks like still rejected.
That’s not an approval till you don’t see ACTIVE status under wearOS. As they approved my screenshot that way but in wearOS still they rejected people can open link and see Screenshots but can’t download watchface as it was rejected because of the screenshot transparency issue
Yes I know that. But the rejected is still from this morning. It always takes something until it is approved there.
If the WF rejects again, I will probably stop working for Wearos until a solution exists. Sorry but I have no time for something like that. It should be a solution from Samsung and Google.
Even my wife said such bare graphics look bad. 
For reassurance, I started adding faces to the Chinese market.
The last three faces have just been rejected for me once again.
The face itself is supposed to be in all the graphics, it looks tragic and comical, but we can’t help it. In this case, you can only replace the graphics without updating the version. I got a separate email on this.
Can anyone explain how to avoid this error ? Your Wear OS screenshots include transparent backgrounds or masking. in proper way what kind of screenshots we should use to make GOOGLE happy ?
My WF was rejected today. Now I uploaded 4 pictures with the screenshots of WFS. Hopefully it fits. I have the feeling Google does not want us developer for WF in Playstore!
I answer and explain what graphics should be placed to be correct.
In the icon field, we put our own graphics with an aspect ratio of 512x512 on a transparent background, without added shadows. PNG or JPG / JPEG format. May be in the watch icon.
My example (correctly goes to the store):
In the graphics field, to be used in other parts of the google store or their applications. Custom graphics in 500x1024. I also post here without shadows, but on my own background.
My example (correctly goes to the store):
Graphics / screenshots section for Wear OS. The so-called 1: 1 graphics, with me the aspect ratio of 450x450. Screenshots taken on the watch, placed in a square with a white background. A minimum of 4, of which the first 2 must be a perfect reflection of the face placed in the store. I do one for each display version: normally 24H and 12H and AOD 24H and 12H.
My example (correctly goes to the store):
Thanks for the explanation. That’s exactly what I did now. But what I do not understand … Watchfaces are approved with pictures of watches and text in the graphics.
This has been the case until now. Now the graphics in the Wear OS section must be clean as a tear 
, i.e. in the form on the watch.
I have seen WF with publication 18.10. and 19.10.
