This is one of the websites I use the most. I use it to find inspiration, assets that I use in other bigger projects, buttons, or even U.I. elements. When I use images from this website my production time is cut significantly I don't have to worry about copyright or infringing on anybody's rights. The membership to this website allows me to use the pictures on various projects I work in.
If you don't feel like you can afford the website membership, you can always buy just the images that you need on a case-by-case basis. You can find almost anything you're looking for in this website if you want to check it out this it right here. You can find more information at Shutterstock.com
If you look around my website you'll notice a lot of the times images have a small caption that says image by Shutterstock. Those are images I got through the membership and I'm able to use them free and clear without worrying about getting sued or infringing on anyone's rights so plan check it out at the very least you can always take advantage of their daily or rather weekly free downloads.