The phrase "a mere image of" is correct and usable in written English.
It can be used to describe something that is only a representation or a superficial likeness of something else.
Example: "The painting was a mere image of the vibrant landscape, lacking the depth and emotion of the real scene."
Alternatives: "a simple reflection of" or "a faint resemblance to".
If anything, what is causing the most fear in our country is a mere image — the graphical image of that up-and-down stock-market line graph, careening over time to new lows and temporary highs.
"Secondary" beauty is a mere "image" or "resemblance" of true beauty.
Or exploit Jenner like The New York Daily News did when it published paparazzi photos on its front page of Jenner alongside the headlines "First look at the new Jenner" and "Bruce in a dress," treating the mere image of a (then still alleged) trans person as a spectacle to gawk at and inviting readers to feel shock.
For many who have witnessed a Streamline hearing, the mere image of men and women shackled at the wrist, belly, and ankles being collectively herded through the legal process is enough to shock the conscience.
Another former G.I., who had been a German prisoner for more than a year, reported to the company a decade later that the mere image of Coke had given him the will to live.
The mere image of Chris Evans and a saddle is enough to turn anyone's stomach.
It seems, then, that he must be aware of a mere mental image of a pineapple.
Its hearty, fist-pumping enthusiasm for criminal individualism is a mere mirror image of the anti-government ideology of libertarian conservatives, of free-market Wild West capitalism, that responds to official crimes with unofficial crimes, and despairs of actual progress through activism.
It must be a mere mental image of a star that he is directly aware of.
He flashed a smile, no longer a mere mirror image of grandfather Matias.
