If you want a B/W image over a gradient, an easy way is to set the B/W pic's layer to Multiply. Then have that layer right on top of the gradient layer. At least that works if what you're talking about is how I picture it.

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.