While I understand the motivation to protect and maximize one's intellectual property (IP), there are times when it's best not to use "one size fits all" solutions, such as royalty free (RF) or stock photography. I cite an instance from several years ago, when an annual report was created, and several RF images were used. One company used an image on their cover, and a similar, nearby company used the same image on the back of their report. Neither CEO was happy, and this is not an isolated incident.
While creating original photography can be expensive, time consuming, and require additional thought and planning, the results can far outweigh the drawbacks. Licenses for that art can be negotiated for a particular period and geographic market, thus limiting the original financial commitment. Should the image(s) be needed for an extended period of time, I don't know of a single photographer that wouldn't welcome extending a license, for an additional commensurate fee. Most will even work out a deal, up front, guaranteeing the rate should additional usage be needed.
Using images from a "pool" of images freely available on the internet, while initially cost effective, quickly lose their punch, when the same images appear again and again on different websites, advertising essentially the same product or service. I cite the proliferation of images used by fractional jet ownership companies that market space available seats on underutilized corporate aircraft. Most of those companies are little more than websites that coordinates open seats, with potential travelers. They own nothing, and have no distinctive culture, especially visual culture.
If a company takes the time, effort, and money to create a "look," they can be handsomely rewarded in that they will stand out in the marketplace. That's one of the reasons why I personally refuse to "wet down the tarmac" when creating an image for a client. It's been done too many times, and has become a visual cliché. Why would I want to create an image that's already been done? It does nothing for my client, other than lump them into a "me too" visual landscape.
To my mind, this is one of the major stumbling blocks of aviation advertising. It's very old school, and stuck in a repeating cycle of visual sameness.
Take a chance, live a little, and open your eyes to what's being done in other industries. Look at automotive photography. It's some of the most original and competitive work out there, and is constantly undergoing change...
Or, keep doing what you are doing, with the same results...