Overall, the web seems to have the mentality of the average 12-year old. And that seems to be what always happens with large groups of people. Sadly, as you present to groups, you have to keep that in mind. Which is why you should look very carefully at what you post.
If you're not a dirty-minded 12-year-old, it may be difficult to image how the web can interpret what you post. When I started teaching, in the '90s, I learned my first lessons about how quickly any ambiguous statement, or image, can be seen as obscene. In fact, I remember teaching logo design and being shocked by some "accidental obscenity" created by students, who had no idea that they were doing a design that looked like a...?
Don't just think twice before you say something, or post an image on the web, think a lot. 12-year-olds don't understand irony, or sarcasm, so avoid it. Maybe you should avoid sarcasm all together, but I digress. And take a look at those images, especially at a glance, and reduced. Does that look like a...? If it doesn't, it doesn't matter. Don't post it.
In addition to thinking before you post something, go back and look it again later. If you are seeing something that you didn't mean, delete it. Don't try to explain it. Delete it. Try again, and be more careful next time.