Isolating the subject
I don't have a hocky picture, but since the holidays are just around the corner, I'll use this nativity scene for my subject. First you'll want to isolate your subject. It doesn't matter if it's from the same image, or a different image, the steps are the same, you'll have to cut it out. Using the Lasso tool or the Pen tool, which ever your program has, get started.
Here, I'm using the Pen tool. For this kind of work, it's much better because it is infinitely adjustable. You can go back and use the hollow pointer tool to modify, and adjust all the curves until they are perfect. In this window, you see the outline appearing in the Paths palette.
The "work path" will remain a work path until you rename it or close the file. If you rename it, it becomes a part of the file and can be re-modified by selecting it in the Paths palette and utilizing the pointer tools to modify anchors, paths or path handles. (The "hollow" pointer tool is the "direct selection" tool which acts upon the elements in the path. Access it by tapping the letter "A" in Photoshop. The Solid tool is the "Path Selection" tool and selects only the entire path and all its components.)
When you have your path perfect, just click the dotted circle at the bottom of the Paths Palette and the path becomes a selection. Return to your photo layer with selection active (Racing ants) and use cmd/J, ctrl/j to lift a copy of the image to a new layer. Diagram Set that layer aside until you're ready for it. (I usually move it to the top of the layers stack where it's safe.)
Preparing the Base Image
Since we're doing this in layers using Photoshop, I'm going to utilize adjustment layers here because they are non-distructive and infinitely editable. To make a monochromatic version of the background for this effect, we'll need to desaturate the image, and brighten the whites so they cut through the color pattern layer we'll be creating next.
Select Layers > New Adjustment Layer > Hue/Saturation, and drag the middle slider all the way to the left. This removes all color. Now, move the "Brightness" slider to the right to brighten the white areas. (If your software doesn't have Adjustment Layers, then just take the image into a new file, convert the mode to "Grayscale" and then drag it back into this file.)