THT has brought to my attention that the new forum truncates pictures that are too wide. The old software 'stretched' but this was deemed to be ugly by the designers.
The good news is the new branding is wider than the old so you are going to get an extra 200 pixels in a week or two. Nevertheless it is best to keep images down to 500 pixels or so meantime.
For pictures that need to be REALLY BIG I hope to be adding some software which will automatically create a thumbnail and link to the bigger picture. I don't know how easy this is but will try it as soon as possible.
Meanwhile forgive the disruption while I get a handle on it.