Hi there, welcome to Aquarium Advice!
Yes, you can indeed post photos.
Here is one method: when you are making a post, look under the text box for "additional options, and then click manage attachments. You can also upload your photos to another website such as photo bucket and link them here. You could also upload your photos to an album on your profile page and copy/paste the link to a thread.
I hope this helps! Thanks for joining the community.