Painting with a vector Icon- Photoshop

you can take a little vector icon and paint with it.
if you start with a jpeg, you need to trace and expand it and get rid of any extra anchor points.
or you can make a little icon with illustrator, (or copy from web)

I took the chicago Loop icon Joe sent me, and first- traced (using color 16),
then "expanded" to let me get at individual anchor points.
then I selected and eliminated (using "A" Direct select tool) the white spaces in between the train routes.
YOu can see where i missed white.

Next> from windows menu drop down, Open up "SYMBOLS"
marquee around icon to select and Drag it into that symbols box. It will be added to whatever is there.

Next> using the spray paint looking thing in the tool box. (shortcut is "SHIFT +S")
Use the top tool- spray.
FIRST select your symbol from the symbol menu, then click on the artboard. Now you can "paint" with the icon, making a pattern.

2. To constrain this pattern in a shape, you will make a clipping mask. it is very easy. see the attached.
select the top layer: "shape to make clipping mask with"- it is a red oblong
Using the shift key-- SELECT BOTH the oblong, and the loop pattern beneath it.
Now hold down the "control" key- to get a drop down menu.
Release at "Make Clipping mask"
You will see the chicago loop pattern below will be constrained to the shape of the oblong.
Try this a few times, by copying some petals.
YOu can also draw a shape with the pen to constrain a symbol pattern.

(Joe, this is the solution if you want to fill your map shapes more with pattern.)
also Tony S., this might be fun for you; your bars could be patterns...made this way... check out other options below the spray paint)....