Without images blog articles would look dull. To have colorful look for an article even if you don’t have an image just do some simple thought process and make your article/post colorful and that too with image.
You can do two things. Firstly, search for an image which is related to a keyword in your article or post, if you don’t find one such image then check if your article have name of some company, organisation, feature that have an associated logo or image etc. then you can use it. Next, you can create your own image for the articles which is contextually applicable.
Other thing that can be done here is that put image ads. With image ads you have colorful layout for your articles. You can give 2-3 images with in an articles depending upon the size of article. The position of ads in multiple ads in an article should be made such that it is not cluttered and article is easy to read.
Give it a try and you will have an image.