Aha! Sorry, I was talking only about posts. There's no way to use attachments with PMs.

I've sent lots of pictures in PMs but the picture has to be on a server, not just on my own hard drive, before I can link to it. One of the ways I've done it is by uploading the picture to an album. There are file size restrictions on album pictures. Last time I checked, if a picture exceeded the limit, the system would try to resize it for you but you might not like the result. I think it might also be possible to get mysterious error messages that don't sound like they have anything to do with the file size (but that go away after you resize your picture).

I think if you make your album "private", only you and your friends will be able to see pictures from it, even if you include the picture in a post. I remember something like that happening to me a few years ago but not the details, unfortunately.

Another way to include your own pictures in posts and PMs is to upload them to a photo sharing site, then link to them there.

Does that help at all?