if you have a smart phone you might be able to upload on your phone.
click "go advanced" then click "manage attachments"
on the popup on your phone click browse and see if you can access your phones pics.
this can be wonky on mobile. not sure if the forum uses an app like tapatalk for mobile, this would make it easier.
on my samsung galaxy s6 i am able to attach pics from my phones camera roll while using the phone.