1. Think up a suitable search phrase e.g. fantasy art and do an image search e.g.
2. roll some dice or use a web one like
3. In this case i’ll use a d20 on the above link to give a row and a d10 to give the column
4. Roll the dice n times and save the image from the row and column specified by the die rolls e.g.
1st roll is 10, 1 so tenth row down, first image from the left
2nd roll, 5, 5 so 5th row down 5th from the left
3rd roll: 8,6
Allow yourself to cheat by 1 i.e. if you roll 8, 6 then choose between 7,6 9,6 8,5 and 8,7
4. When you have a big enough collection build a campaign setting out of those images.