Using social media brands (logos) in academic publications
I guess the answer subjective but as far as I'm concerned it's totally fine to use logos.  I've done it myself*. In the caption you can make it clear they are just examples. Of course there are some exceptions.



Regarding your concerns:


  it may be considered a promotion or endowment of mentioned brands.


It's fine you take well-known brands.


  it may be considered unprofessional.


No (at least not in my research community)


  it may loose relevance with time


That's life. The entire paper is likely to lose relevance as well.



*Example: