Barrow Bay Landing Stage, Derwentwater, English Lake District. Sands at Low Tide, Applecross Bay, North West Scotland. Camels below 'Ridge of Needles', Jebel Sahro, Southern Morocco. Shkoor Ali points the way, Biafo Glacier, Karakoram Mountains, Pakistan. You can take pictures yourself, or commission a photographer to do so, but in many cases the images you need already exist.
Libraries remain the most straightforward and cost-effective source for many images.
Some of these are of very high quality, others less so, and if you are a frequent user of images, it may be worth paying the initial purchase price for the collection. But by their very nature these collections tend to be full of generic 'lifestyle' images and to cover the more obvious locations. And, by their very nature, you will never know in advance who else has used or is using the very same image. This is where picture libraries come in. If original transparencies are sent, so that you or your printers can scan them exactly as required, these will be on loan and you will be responsible for their safe return.