Main app's icons overlays in Nova Prime's widgets I've been using Nova Prime for about 5 years, which includes doing at least 10-20 settings backup-and-restore on various devices.
Today I made one another (on my Motorola Moto Z2 Play / Android 8.0 Oreo) and to my extreme surprise I have noticed that all my (restored) contacts widgets have a nasty &quot;main&quot; app (i.e. Contacts) icon overlay over each my contact's photo.
Picture worth thousand words -- before (left) sending Z2 to repair and after getting it back (right):

Analysis so far:

the problem is only with Contacts; other widgets (Wikipedia and Fancy Widgets in my case) have no &quot;main&quot; app icon overlay,
happens on both widgets restored from Nova Prime's backup and freshly added,
happens on Motorola Moto Z2 only (i.e. does not happen on Motorola One),
happens on Motorola Moto Z2 only this time (starting from this backup restore), since I hadn't this problem for past half year, prior to sending this phone for a repair.

Questions:

does anyone else experiences similar problem?
what is its source: is it caused by recent change to Contacts or Nova Prime?
is there any workaround or a way to get rid of this nasty little thing?

I am adding a contact-shortcut widget by:

opening Contacts app (default app under 8.0 Oreo?),
finding given contact and tapping it to get to details,
tapping three-dot and selecting Create shortcut from menu.

The only difference that I noticed is that prior to this backup restore (prior to sending my Moto Z2 for a repair and getting it back) and on every other device I am getting shortcut created right after above (right after tapping Create shortcut). While this time and on this Moto Z2 I see some new, additional Add to Home screen window, where I have to tap Add.
I assume (given above) that the problem's source is Nova Prime, not Contacts app.
I am using Motorola Moto Z2 Play (XT-1710-09) with Nova Prime 6.0 on board Android 8.0 Oreo.
what is its source: is it caused by recent change to Contacts or Nova Prime?


Rahul in comments has pointed the reason (thanks Rahul). It is an OS feature introduced from Oreo (and the likely reason you didn't see it earlier- service folks must have upgraded it while under repair). For more see Android Developers : shortcuts overview  


  is there any workaround or a way to get rid of this nasty little thing?


Long press on shortcut &rarr; edit &rarr; long press on photo &rarr;select theme  &rarr; Gallery apps &rarr; select photos and choose the contact photo, go back  &rarr; Done

A disadvantage is that you have a rectangular icon that won't match with other icon appearance . But that may be good too to differentiate contact shortcuts! 

I don't know how to fix that, unless you use a photo editor app that gives you round shapes (OP has suggested - you can use this Ukrainian on-line tool or this Russian on-line tool or search for some alternative).

And it is not for contacts only. I have a mail app which shows the same for "compose" shortcut. This app is targeted for min sdk 28 (Oreo). From August this year, all apps have to target Oreo and you will see this behavior uniformly

Tested on the latest version of Nova on Pie.