I just looked at all attachments that are there at the moment: there are 6000. From that 6000 are 17 that are bigger than 200kb. You are correct about the 20mb max on your account, but there is a max of 200kb per post. That has been larger, then from time to time Jaap or me had to download all big pictures, resize them and upload again. Otherwise available webspace would have ended a long time ago. I sugest you resize the pictres to 1024x768max size before uploading. You don't have to buy anything for that, if you have XP, you can download a image resizer tool from the Microsoft site. Other tools like infranview can do that too, that's freeware.
To try I let xp resize your biggest picture, that was 900 kb, now 166kb