Can we generate signals in reality that have non symmetric magnitude spectrum in the Fourier domain?
As @Bob said, it depends of your definition of &quot;in reality&quot;. I am going to ignore images on this post and focus on signals as a function of time.

One-dimensional signals always have a symmetrical magnitude spectrum. Examples are the voltage or current on a wire, or a sequence of real numbers stored in digital memory.

Two-dimensional signals may have a non-symmetrical magnitude spectrum. Examples are complex signals, whether defined mathematically or stored in a digital memory; and the voltage or current on two wires, one of which is labeled $\sqrt{-1}$ and with the agreement of doing complex arithmetic (see $9\rm V$ Battery with $45^\circ$ phase).


In my opinon, all these signals exist in reality, and then the answer is that yes, some signals in reality may indeed have a non-symmetrical magnitude spectrum.