Is this normal for the tabs

Dunno if it's normal, but I get it too.

It's a long standing issue, going back at least to 2007, according to a forum search. No fix or work-around that I can find. Sorry.

Post screenshot so we can know what you are seeing.

Can you modify the icon through ObjectDock to something better?

Yes, you can change the icon and I was able to use one of the bundled images from OD itself.

I don't use Object Dock, but I do make docks. So I thought I'd try to help. 

There have been several threads on this over the years, with no support response, just saying.

https://forums.wincustomize.com/312572

https://forums.wincustomize.com/168322

https://forums.wincustomize.com/381435

I had a Outlook 2010 pdf that I dragged into the tabs and it was like I said a black square. I did a Google search for the image of the cover of that book and used the Icon Developer to make a icon of the book cover. I Tried what RedNeckDude suggested and it worked perfectly, now instead of a black square I have the cover of the book.

Thanks !!

Well, there was that work-around but you will need to do that for each file.  It seems to me that OD should use the icon included with the program. It's right there in Bundled Images.

I blame adobe.  They.d mess up a dream.

Ahaha. Zubaz, I blame Adobe too, as I've run into this myself.

PDF thumbnails are unique in that they have all the alpha bytes set to 0, so the image renders fully transparent or all black. Before converting the GDI bitmap of a thumbnail into a GDI+ bitmap, I make a quick diagonal scan of the thumbnail: if all alpha bytes are set to 0 I convert using GdipCreateBitmapFromHBITMAP, which throws away alpha information:

            ' Do a quick diagonal scan to make sure not alpha bytes are set to 0.
            ' Otherwise PDFs thumbnails and videos thumbnails under XP are rendered
            ' as fully transparent. If all alpha bytes in our scan are set to 0,
            ' then render using GdipCreateBitmapFromHBITMAP.
            
            Do While X < BMInf.bmWidth And Y < BMInf.bmHeight
                If BMData(Y * BMInf.bmWidth + X * 4 + 3) Then
                    IsAlphaBitmap = True
                    Exit Do
                End If
                Y = Y + 1
                X = X + 1
            Loop

You might want to tell Jeff about this, assuming he doesn't know about it already.

Thanks for being a friend Jorge.  My life is better because of you.

I'll second that.

I'll third it!!!  Jorge is a great guy who is always there to help.