Definitely, if you aren't sure that you are comfortable posting pictures, don't post them. I have always assumed that if anyone really wants to find anything I have ever put online, then they can. There is no way to completely hide something once it's been online.
That said; before transition I think I only ever put 3 pictures of myself online. Once I begin to transition however, I began to feel more comfortable with myself and put more and more photos online. When I went full time and started hanging out in my local queer community and dating some amazing trans women, I started to realize that for me and my circumstances, I didn't care if people saw my photos (whether just portraits, transition related, or even 18+ stuff) All of my friends and partners know me, and would just like me more the more photos they see, and I'm lucky to have an accepting workplace and family. Anyone who doesn't approve of the photos I take and the things I do isn't someone I intend to interact with.
Anyway, that's a long winded way of saying: only post photos if and when you are comfortable with the fact that anyone could potentially see them.
-Molly