Pics are probably best loaded as .jpg, but they need to be trimmed so that the longest side is a maximum of 1500 pixels and the overall file size is less than 976.6 kB. One of the tools on the toolbar is for inserting images. Maximum of 5 images for post. If an image doesn't seem to be loading, it's probably too large in one of those areas.
If you press the 'advanced' button when posting, you get some more options, plus you can then 'preview changes' to view your post to check that the pics are displaying properly. Also under the advanced settings is a 'manage attachments' button, under which you get more details about what files can be attached and their maximum file sizes.
Last edited by Simon Barden; 04-12-2016 at 04:53 AM.