When you add a photo, you are able to enter in a description of that photo. When users use the search function, it searches the content that is written in the description, as well as the galleries themselves. This means that if you cannot find a gallery that perfectly describes your photo, you can add keywords in the description and that way users searching for this type of photo will come across your photo in the results. So if you have a photo of your cat on a pillow next to a tree in the city, you will want to not only choose the appropriate categories when posting the photo, but you will also want to write "cute, cat, pillow, tree, grass, etc" in the text area describing the photo so that people that search for "cute cat" will come across your precious little animal!
Please do not upload photos that are over 200 kb. This is plenty of space for web-optimized photos. If your photos are larger than this, it means that you must first optimize your photos using some sort of photo editing software. We limit the size of the photos because this is a free service, and storage space and bandwidth can get pricey very quickly when users are careless about the size of their photos.
Each user gets one "photo album". We suggest that you name it something like "Username's Album", but you are free to call it what you like (no profanity, please).