1. Quality. Search engines will scour the internet for any images they can find which may be related to your enquiry. These will generally have been optimised to fit onto a web page. That is, they will be low resolution 'thumbnail' images specifically designed to be viewed on a small monitor.

When you blow that image up to fit on a Powerpoint slide, you'll find yourself with something blocky and distinctly amateurish which will detract from the information you're presenting.

2. Copyright. Google Image searches will list *any* images it can find. As such, they are likely to contain a lot of copyrighted material which you have no right to lift and use in your presentation. It only takes one email of your slides to an interested audience member and they could easily end up in the public domain, with or without your knowledge. If those slides contain copyrighted images, you could find yourself in hot water.

Even if you vow never to email your slides to anyone, there's no sense in getting in bad habits you'll just have to undo later. Learning how to use images properly gives you the skill you'll need for a publication or big conference presentation.

3. Ditch Google, get Creative. Images under Creative Commons (CC) licence are your friends. There are a variety of licences under the CC umbrella, but as long as you credit the image creator (generally, the photographer) and aren't planning to do any major re-editing of the original, you'll be OK to re-use any images with a CC licence.

Where to find them? Flickr has a huge range of images, many of which are Creative Commons. A good way to search them is through the Compfight search engine. Just click on 'creative commons' in the sidebar, enter your search term and away you go. Clicking an image takes you to its Flickr page:

Check the image licence (1, above) - it's summarised on the page but you can get more details by clicking through. This one says you are free to copy and transmit the work as long as you attribute the creator of the image, don't use it for commercial benefit and agree not to alter it.

Then move up to 'actions' and click on 'view all sizes' (2):

Then just download (4) and paste it into your Powerpoint with some text crediting the image. For this image I would suggest: Flickr user 'mobile disco': "I Love Peckham post-its" (there's no real name given for this user, if there is one, use that instead).

Ta-da! You have a high quality, correctly licensed image from the very creative Flickr community, rather than the lo-res, copyrighted fare of Google Images.

Further reading:

11 ways to use your image poorly - classic Presentation Zen post on the best way to use your image in a slide (hint: *fill* the screen).

Easy-peasy guide to crediting images - great flowchart to help you check you're doing it right.

Where can you find good images? - more Presentation Zen goodness, list of alternative sites for good, roylaty-free images.