Format & example of how to cite an image from the web:
Artist Last name, First & Middle initials. (Date, or n.d.). Name of clip art or stock image [Type of image]. Site. URL
Winn-Boujnida, C. (n.d.). White table lamp on gray end table [Stock photo]. Unsplash. https://unsplash.com/photos/jhDof9B6vPY
AnnaliseArt. (n.d.). Balloons [Clip art]. Pixabay. https://pixabay.com/illustrations/balloons-confetti-celebration-4022896/
Note: Although for most images you must look at the license on a case-by-case basis, images and clip art from programs such as Microsoft Word and Microsoft PowerPoint can be used without attribution.