Don't be penny wise and pound foolish
Make sure you have the rights to EVERY image on your site
Grabbing an image from the Internet and putting it on your website is 'free' when you do it, but could end up costing you dearly in the long term.
Photography companies are agressively protecting their copyrighted images. They have programs that search websites and compare the 'digital fingerprint' of each image to see if it matches any image they have. The software is so good it even detects partial matches. Cropping an image and/or changing colors a bit will not keep it from being matched.
If you are cuaght violating image copyright, you will most likely get a letter from an attorney insisting on compensation in the hundreds of dollars for each time the image is used on your site. We know of several instances where companies had to pay thousands (and one case tens of thousands) of dollars for copyright violation.
If you are using other people's images on your site, make sure you have written permission (emails are fine) from the copyright holder and keep those in a secure place.
If you need plant images for your website, they are available for purchase from a number of sites. When you compare licensing costs to the cost of fines for one non-licensed image, it would be penny wise and pound foolish to grab images from the Internet without permission.