When I first started blogging, I used Google to find pictures. I knew I might eventually run into copyright issues, so I stopped and looked for other options. Below are my notes from the research I did about sites that offer royalty free pictures.
One side note: Before creating an account on photo sites, I hardly ever received spam e-mail. Now I receive spam mail every single day. Make sure you have a good spam filter on the e-mail you use to register on these sites. I'm not sure which of the four triggered that: Deposit Photos, Fotolia, iStock or Dreamstock.
What's Royalty Free?
According to this article from Stock Photo Guide, royalty free is "a type of license that gives you permission to use a stock image in certain ways. Royalty free means you are not required to pay a royalty each time you use an image."
Royalty free doesn't mean we can use the pictures whichever way we want. Some licenses may not allow you to use the pictures for commercial purposes, for example. Others may specifically state that the pictures cannot be modified. Each site has its own specific rules, so make sure you read the license carefully before using any pictures, even when they're free.
Pictures on Flickr are free to use, but require you to credit the author by linking back to their profile. This article on Skelliewag.org gives advice on how to find and use images on Flickr.
[The article mentioned above is no longer available, but you can find Flickr advice here instead. (edited 3/28/17)]
Users can search images within six types of Creative Commons copyright licenses. To be on the safe side, search for images within the Attribution License, which allows you to modify the images and to use them for both commercial and non-commercial purposes. The other five licenses are more restrictive.
I never use Flickr, because I don't want to bother linking back to that site every time I use a picture, and I found the quality of pictures was generally lower than on paying sites.
MS Office Clipart
I occasionally use MS Office Clipart pictures when I'm in a hurry to find a picture. I tried to find out if it's okay to use them for blogging, but every answer I find links to this contract, which is very tedious to read. I'm assuming it's okay, since I'm not using them for resale or business purposes.
Most of the time, I use Deposit Photos to find pictures for my blog. This site doesn't offer free photos, but I always find a good selection of pictures on that site for only $0.50 each. I don't mind paying for getting exactly the picture I want. The minimum purchase is $10.00 for 10 credits, and all the pictures I bought so far cost 1/2 credit each.
Fotolia Fotolia offers some free pictures, but most are sold for 1 credit or more. The minimum purchase is 10 credits at $1.30 per credit (cheaper for greater quantities). A bit expensive compared to Deposit Photos.
Dreamstime Dreamstime offers free pictures as well, but most of them cost credits. The minimum purchase is 8 credits for $9.99, which is good for up to 8 pictures. It all sounded good, so I registered and bought some credits. There was a catch, though. In order to download any of them, even the free ones, I was asked to update my profile information, including my first and last name and my mailing address. I became very suspicious of that site for this reason. Why would they need my mailing address? I'm thinking I'll probably start getting a lot of junk mail if I enter it. They'll let you create an account and buy credit by just entering your e-mail, but then you can't use it unless you complete your profile information. Hmm... Fishy.
iStock Photos iStock Photos doesn't offer free photos, as far as I know. The minimum purchase is 6 credits for $9.99. I found it a bit pricey, although they have a good selection of photos to choose from.
Articles About Finding Royalty Free Pictures
I know there are a lot more sites out there where bloggers can find royalty-free pictures. I haven't looked into them because the sites I've found so far are enough for my needs. For further research, I suggest you read the following articles.