I'm putting them as attachments in my travel thread, partly because it keeps them easily visible with the post and partly because there is no Mongolia gallery to put them into anyway.
If one isn't supposed to be putting photos as attachments then what is the purpose of having a way of attaching them?
Okay - a travel thread is an acceptable place for attachments, you could also request a Mongolia gallery though! My point was that I don't want people uploading zoo photos as attachments in lieu of putting them in the gallery.
Either way, there is a limit on how large photos can be when uploaded as attachments - unlike the gallery, there is no auto-resize facility for images uploaded as attachments.
I've removed the limits on the dimensions of the image (theoretically you can upload a 50 megapixel image), but there is now a limit of 2MB on file size for attachments.
You either need to reduce the quality - JPG quality of around 70 is more than sufficient for web use and 4000x2500 images should typically be less than 500KB in size anyway ...
... or resize them down to something reasonable for viewing on a website. There's no point uploading full sized photos, since even the highest resolution 30" monitors are only around 2560x1600 resolution.
Uploading full sized high resolution JPG images is only going to take up more space on my servers (and cost me more for backups!), and more importantly, is just going to slow things down for everyone (both for yourself uploading them, and for everyone else viewing them).
My suggestion before uploading, is to resize your photos to something sensible like 1600x1200 (more than enough for 95% of web users) with a JPG quality of around 70 to shrink the file size.
These are the settings I use for photos I upload to my personal blogs and the JPG files are generally between 200KB and 500KB in size.
I use Adobe Lightroom to manage my photos and I have some export presets ready to go for uploading to websites, so it's simply a matter of choosing the photos I want to upload, then exporting them all in bulk at the settings I've chosen - it resizes them and sets the quality automatically, it literally takes only two clicks to do it all for me and make a copy of the files ready to upload to the site.
Note that the gallery doesn't have this size restriction - it will resize photos automatically for you when you upload, so uploading full size high resolution JPG images to the gallery won't cause any problems at my end - it will just take you longer than if you resized them down first.
Also note that the next version of ZooChat (using XenForo forum software) will have auto-resizing for attachment uploads, so that will make things a bit easier in the future too.
Just FYI - for those of you with very slow links, I've also tweaked some of the settings to allow more time for the upload to complete before it times out - that should hopefully prevent a few more errors too.