Here is another possibility if you really want to use Graphics3D
with 2D contour plots. I think MarcoB's answer is probably the best, but it might depend on exactly what you're doing with your data.
I define dat
to be the data you linked to on PasteBin.
plot = ListContourPlot[dat, AspectRatio -> 1/2,
ColorFunction -> "TemperatureMap", PlotRangePadding -> 0]

Show[
Graphics3D[{
Texture[plot],
Polygon[{{0, 0, 0}, {2, 0, 0}, {2, 1, 0}, {0, 1, 0}},
VertexTextureCoordinates -> {{0, 0}, {1, 0}, {1, 1}, {0, 1}}],
Texture[plot],
Polygon[{{0, 0, 0.5}, {2, 0, 0.5}, {2, 1, 0.5}, {0, 1, 0.5}},
VertexTextureCoordinates -> {{0, 0}, {1, 0}, {1, 1}, {0, 1}}],
Texture[plot],
Polygon[{{0, 0, 1}, {2, 0, 1}, {2, 1, 1}, {0, 1, 1}},
VertexTextureCoordinates -> {{0, 0}, {1, 0}, {1, 1}, {0, 1}}]
}],
Lighting -> {"Ambient", White}
]
Using the Texture
option in Graphics3D
, I can add the plot as the texture of a 2D polygon in 3D space. I believe it will stretch the texture to fit the polygon as long as you specify the VertexTextureCoordinates
to be the 4 corners.

Of course you can make the white border transparent if you prefer, and other tweaks like changing the aspect ratio, etc.