Give a pixelated effect to your images in fireworks. Following are the simple steps.

Step 1

Open the image.

Step 2

Use Filters>Alien Skin Splat LE>Edges to give the edge mode.

Step 3

Select Pixels in Edge Mode

Step 4

You can different values to Edge Width, Margin and Feature Size sliders. You can check or uncheck the option Transparent Fill.

Step 5

The final image is a pixel edged frame with a transparent fill or without a transparent fill.

See below an image in a pixel edged frame and unchecked the transparent fill option.