[NTG-context] Working with layers ... with example

At http://ideone.com/D6Mmj3 there is the title page for my document. I want to place the table in the middle of the A4 page (horizontally and vertically) and the logo beneath it, preferably at the bottom of the page. When I failed to get the table placed where I want it, at some point, I tried to use a layer. In the end the table was placed okay, but in a messy way I suppose. Now I have tried to add another layer but the logo appears to the right of the table or not at all. As far as I understand there can only be one background layer, so that trick with the table will not work again for the logo I guess. Can someone please help me to use multiple layers that I can exactly position?