Have a ton of GFX with alpha channels and black fill - basically black on black. I cant see what these are unless I drop them over footage in a timeline -

Anyway to show these in the preview monitor and actually see these images

Unfortunately, not that I am aware of. I've run into the same issue in the past.

What I ended up doing the one time I had this issue was also creating a series of comped versions of the graphics over white with the same name (but JPG instead of PNG). Then I imported both and sorted them in a bin - I cuold easily open the 'visible' version and check it before cutting the alpha version into the edit.

Not really a solution, but a workaround that was satisfactory for the one time I've run into an issue like this

Possible idea 
Setup  a timeline with white(?) graphic on V1 and all your graphics on V2.
Load timeline into the Source window.
This would allow you to flip between Source and Record monitors (Mapped to KB) to Scan / scroll the titles in the Source monitor for preview and or IO selection. Select V2 only in the source you can edit staight into your edit.

I suggest having a V3 track with markers to locate GFX I wanted to use. (Helped with having "Go to Previous" and "Go to next marker" mapped to my keyboard.
Naming the Source Titles Timeline something like "01 titles" as it will then appear first in the Source drop-down menu to select loaded clips.

Thats what I was thinking of doing.

thanks

Create your graphics in Photoshop or similar with the artwork on a layer over a white background.  Import them as sequences with alpha support.  The sequence will show your graphic, with the logo on V2.  Either use the appropriate layer from the bin or just use V2 as your source when editing the graphic into your production.