Instructions
Go to google.com. Select the "Images" tab. This will ensure you only receive images during your search.
Create you keyword list. Start the list with the broadest words that describe the picture you are looking for. For this search the words "Black and White" and or letters "B&W" is a good starting point. This will return only black and white images. Type a comma. Type your idea of a religious symbol. Maybe you are looking for a crucifix or some other symbol -- type this.
Click "Search." If the pictures are not exactly what you are looking for, or the search returned too many images, refine your keywords to improve your results.
If you want something more personalized, visit a local photographer and tell them about your ideas for an image. They will be happy to help you.