Rule #1: Do what you gotta do.*

*That said, I have noticed that Instagram users tend to prefer the personal nature of the images they see. Once someone starts hawking their wares or services, I tend to unfollow very quickly. Maybe make the work posts somehow more personal, and I think you'll be fine.

I've taken a photo of a design and uploaded it to my Instagram. If you tag it correctly, you'll probably get some feedback. I tend to stick with Dribbble, though, since most of my job opportunities have come from shots that I uploaded to my Dribbble profile.

My brother is a game designer and went on Instagram to show the 'life' of a game designer. He usually gets a ton of likes/feedback on his pics of development engines , testing things at 3:00 AM, doing 'creative sessions' at coffee shops and such. His biggest fan is surprisingly a 50 year old retired marine from the US.

After his success I decided to use Instagram to mainly show our studio culture. Like, parties, birthdays, events, behind-the-scenes etc. . I mostly find it works well as just another way to keep in touch with business partners and existing clients (to show you still exist and do things) but I don't recall ever getting a new client with Instagram.

People mostly seem interested in what others are up to at work and webdesign, gamedesign, UX design etc. are often more 'interesting' to them than other jobs.

It works really well for illustrators and logo designers, I know I following a bunch just because they ONLY post their work and no crappy photos.

It depends on your audience/followers. Most of my friends are designers and artists. Most, if not all of my followers are also designers and artists. I only post the things I want to post which is mainly my work, that's why they are following me. I've definitely gotten work through Instagram on multiple occasions but not intentionally. But I'm mainly referring to my personal account. If you want a separation of concerns, try creating a business account. Most agencies do!

Shameless plug lol: lets chat on IG! @crookedpixel

My career started largely because I posted on Instagram a lot and it did well, but that was my use of Instagram since the beginning. If you have been posting all personal pictures and you are followed by your friends and family, I don't recommend suddenly posting work. Instagram makes it really easy to have two accounts though, so you could have an Instagram account of curated work and keep your personal account separate.

That being said, I don't think many agencies owe their successes to Instagram, and likely have other goals from it's use besides gaining work opportunities.

Have friends who run graphic design agencies that find it useful to promote work this way, especially successful for packaging jobs. As a UX design agency we find it more useful to post culture/team shots, behind the scenes stuff. Don't expect to ever get work directly or even have clients follow you - mostly aimed at peers and promoting general brand awareness activity. Definitely would not spend a large amount of time on Instagram, it's a luxury if you can find the time in my opinion, but a good string to add to your social media bow if you can justify it.