Determination of brominated aromatics by 13C and 1H NMR spectroscopy
I don't find any experimental spectra online, but I have been suggesting NMRDB.org to students and colleagues. I don't know how accurate the predictions are, but the site is easy to use and for the compounds you're suggesting, rule-based methods should be fairly reliable.


Predict $\ce{^1H}$ NMR
Predict $\ce{^13C}$ NMR


In the 4,4’-dibromo-N,N’-diphenylhydrazine, you should have two sets of "double doublets" (i.e., four peaks in each set of equal height).



In the 4-bromoazobenzene, you break symmetry, so there should be four signals which integrate to two protons, and one additional signal integrating to one proton (i.e., all ~7.3-7.8 ppm, so a big mess). 



In the $\ce{^1H}$ spectra of 4-bromoazoxybenzene, the protons closest to the azoxy -N+-O- should be deshielded a bit (maybe ~7.8-7.9 ppm?) compared to the aza analogue. Certainly it's also going to be a fairly congested spectrum.

I'll leave the $\ce{^13C}$ NMR as an exercise (or to others to answer).