Layer the objects so those that should be behind other objects are in layers below them in the Layers palette (see Figure 6). After all the objects are in position, start blending them into a cohesive image. One blending method is to paint a semi-opaque mask on the layer. To do this, select the layer, click the Add Layer Mask icon, and paint. Use black paint to remove the image and white to paint it back; vary the opacity to smooth the image edges.
Figure 6 Arrange objects in layers so that those in the front of the image are the highest layers in the Layers palette.
You can also use texture brushes by clicking the Brush tool and choosing a brush shape from the Brush drop-down menu (see Figure 7). Open other brush collections using the Load Brushes menu option in the brushes palette. Use textured brushes to paint onto masks and as brushes to use with the Eraser tool. Add a new layer and use a textured brush and a suitable foreground color to paint onto the image.
Figure 7 Use textured brushes to erase around images and to paint onto the images.
If you prefer that an item appear dimensional rather than blended into the rest of the image, add a drop shadow to it to suggest layering. Click the layer and add a drop shadow layer style, adjusting the angle of the light to match other objects in the collage.
Figure 8 Use a drop shadow layer style to elevate an item above the remainder of the collages and add dimension.