How to support SNOT and is there another way to support this mosaic?

I'll try to explain this as best as I can. Originally I was simply going to have some plates on top of a baseplate, with a mosaic image next to that plate.

--   plate   --   |   --   mosaic  --
-- baseplate --   |   -- baseplate --

I wanted to build an image at the same level next to it. I could build a simple mosaic with just 1 x 1 plates, but it would look better if I did a side mosaic. However this raises two problems:

1) Part of the images, the longest point would be 25 plates/10 bricks long. Do you guys think I'll need to support this somehow along the middle? If so, how can I support them? It's only a very small gap underneath.

2) In order to keep the mosaic and the original plate level, this means I have to raise the plate so that now it looks like this:

--   plate   --   |   --  brick /w hole (technic) for SNOT --
--   brick   --   |   --  plate  (to keep both sides level) --
-- baseplate --   |   --  baseplate --

This doesn't seem very efficient, since I would have to end up raising multiple plates around the mosaic, but I can't think of any other way.

Thanks for all your help!