Basically, it should be just a matter of changing STREAM resource 1192 in a copy of aero.msstyle to be an updated PNG file, right?  I want to keep everything else the same as aero.theme.

 

With Big Muscle's UxThemeSignatureBypass DLLs loading, it seems I could make a new .msstyles file with the updated resource, then define a .theme file to reference it, right?

 

So I tried it...

 

• Started with a copy of Win 10 build 10130's aero.msstyles file
• Renamed it to:  Rounded.dll
• Replaced STREAM resource 1192 with my own theme atlas file, crafted to have all the graphics in the proper positions (they haven't moved for a few builds now). 
• Saved the result into Rounded.dll
• Finally, I renamed Rounded.dll to:  Rounded.msstyles
• Copied Rounded.msstyles to the folder: C:\Windows\Resources\Themes\aero
• Edited C:\Windows\Resources\Themes\aero.theme to refer to Rounded.msstyles where it had aero.mssytles before, and to use name Rounded instead of @%SystemRoot%\System32\themeui.dll,-2013.
• Saved the edited result as Rounded.theme

Now I can select the Rounded theme from the Personalization panel, and it appears to load (it loads the background image I chose), but the theme atlas resources are not those I placed in the file. 

 

Any ideas what I might've missed?

 

-Noel

Have a look here. At least in Windows 7 is where your themes are saved.

%LocalAppData%\Microsoft\Windows\Themes

Try customizing your theme in the Personalization panel, save it and then look at that path in Explorer. This may give your a theme that has been processed by the Personalization panel process. I have no understanding of your dll or the msstyles files and thus is out of my scope.