When using BitmapSource.Create() you should provide the raw pixels of the image without any file header. And the format and stride should match (for example, Stride=Width*4 and Format=RGBA8).
Could you verify that the input to that method is correct?

Thanks for the reply and guidance. I was able to make this work by changing the code per your suggestion:
BitmapData sourceData = b.LockBits(new System.Drawing.Rectangle(0, 0,
b.Width, b.Height),
ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
byte[] sourceBuffer = new byte[sourceData.Stride * sourceData.Height];
Marshal.Copy(sourceData.Scan0, sourceBuffer, 0, sourceBuffer.Length);
b.UnlockBits(sourceData);
ImgSource = BitmapImage.Create(b.Width, b.Height, b.HorizontalResolution, b.VerticalResolution, sourceBuffer, sourceData.Stride, BitmapSource.Format.BGRA8);
b.Dispose();

I saw other posts where you are suggesting that using a FileTextureProvider is the way to go when trying to dynamically load images and I maybe that approach would better fit our requirements. Is there a way to use multiple FileTextureProviders and decide which one to use depending on some criteria?

Thank you

Yes, you can have your own FileTextureProvider. For example, depending on the Uri format, or if the file is available or not, you can decide whether to use your custom implementation, or just fallback to any other implementation (similar to what we do in our EmbeddedTextureProvider: https://github.com/Noesis/Managed/blob/master/Src/NoesisApp/Core/Src/Core/EmbeddedTextureProvider.cs).

Regarding the issue about the BitmapSource, can we close this ticket?

Yes, thank you. I found a way to render the bitmap so you can close the issue.