The above data is the is the anisotropy of temperature of the Cosmic Microwave Background (CMB) as measured by NASA U2 airplanes in the 1970s.
The anisotropy is due to the redshift and blueshift of the Earth moving 300 kilometers per second or 1,080,000 kilometers per hour relative to the frame of the CMB, in the direction of the + at the center of the red region of the plot. This is mostly due to the peculiar motion of the Milky Way toward the Great Attractor.
This anisotropy is usually subtracted out in the data you see nowdays, but it is still there in the raw data.
So, yes, the CMB is used as a standard frame of reference. Even though all light moves at the same speed in a vacuum, there is redshift and blueshift of the CMB due to motion relative to its frame.
Note: in the plot red means hotter and blueshifted, blue means cooler and redshifted.