Every picture (or other intellectual property like a piece of text) is practically copyrighted by default. There are certain exceptions and variations by country, but for someone who needs pictures for a business blog post, e-book or similar widely distributed content, it's better assume everything is copyrighted and act accordingly. You cannot just go to Google and use any image that feels right for your purpose. You need a permission to use it. As it's usually too much hassle to ask the photographer directly, you are likely to select photos which are already licensed so, that you can use them for your purpose, or you can easily buy a license from a stock photo web site for few coins.
To say it again, never use a photo in a business blog or paper unless you are sure you have a right to use it in the intended purpose. Either it's released with an open license such as Creative Commons (CC-logo), or you have bought a license. And not just any Creative Commons or stock photo license, but one that allows you to use it the way you want to use it. Some Creative Commons licenses allow non-commercial use for free, but not commercial. Many stock photo licenses allow use only once!
But luckily there are more and more free images available every day. See e.g. https://blog.bufferapp.com/free-image-sources-list for a good list of free image sources. And paid images are mostly quite inexpensive nowadays. The price of an image is often small compared to the search costs, that is your time, which for your business is not free.
Finding the right image may be quite time consuming. You have a vision of what you are looking for, but never seems to find anything suitable. 10 minutes turn into 2 hours of frustration. It's kind of like shopping really. You start with high hopes, but come back exhausted and empty handed. This is especially true on business-to-business context where markets are quite niche from photographers' point of view, so there is not much supply.
It's usually easier to approach the imaging needs from different perspective. Rather than trying to find a descriptive image that suites your title, it might be better approach to have something that just sets the right feeling. Add some texts and graphics on top of it, let say, make a image with title for the post. Canva.com is a great tool for that. And you can also buy images from Canva for 1 USD each.
The best approach for long term is to build your own collection. You have a smartphone with camera that is perfectly ok for all content marketing needs. And so does all your team members. Get your team use that camera to shoot pictures in everyday business situations. It takes bit of effort to develop eye to spot the opportunities, and it's always bit of an hassle to stop for that 30 sec to shoot the picture. But that's a way to build your business a internal stock photo collection that will make everybody's life so much easier when creating content for blog posts, papers or presentations. These photos are unique, nobody else is using them. They are perfect fit for your business and industry, as they have been taken in day-to-day business. But remember to ask everybody to give your company the appropriate rights when they submit anything for the collection unless you have appropriate intellectual property clauses in employment contracts. You may also collect great images you find online, but be sure not to collect anything you don't have a license to use.
