Acobox is a great place to find blog pictures. Signing up for an account is absolutely free and only takes a moment. They have quite a nice selection of images that already optimized for blogs. The images are categorized so you can easily browse through the selections they offer. But the best part is that you can search through all the photos using a keyword or phrase. When I searched on the word "lily" I came up with the following images:
Once you have chosen an image to use, the website makes it super easy to copy and paste the code right into your blog entry. You can choose the size and the alignment that you would like for your photo and it provides the HTML code you need to make the image appear.
Another nice thing is that the image is hosted by Acobox and you don't have to worry about going through the hassle of uploading the photo you want. The images also have all been properly licensed and as long as you follow the rules they lay out in their Terms, you don't have to worry about copyright infringement.
As a photographer, you can upload your photos to Acobox to offer for use by bloggers. It's a great way to build up a reputation as a photographer or just to share some beautiful photographs that you would like other people to have a chance to use.