There are three important factors to assess when selecting an image. color, tone and overall appearance.
You can find a high quality image by searching for a larger size. For example, Google Adanced Image search allows you to narrow your results by image size.
Through a Google Advanced Image Search, narrow your results by the usage rights drop down menu and select the appropriate license:
Free to use or share
Free to use or share, even commercially
Free to share or modify
Free to use, share or modify, even commercially
An image should ideally have a resolution of 250 dpi (or dots per inch) to occupy the printed page. Larger images found on the internet typically have a resolution of 240 dpi. This is certainly fine to print.
If your image is 1024 x 768 then you would print no larger than roughly 4 x 3 inches.