You have an equal quantity of storage available at your Gallery that probably is going underutilized. Want an image in a thread? Upload that image into your Gallery and then link the photo at the post in question.
For instance, this photo in my gallery -- Glacier N.P., Many Glacier Area
Through the 'manage attachments' link under the posting window, if I try to put the above page link into 'Upload File from a URL' I receive an 'Invalid File' response. You need to extract the actual URL of just the image.
On a PC
, right-click on the image and select 'View Image Info' from the menu that opens. Copy the image 'Location' link and paste that URL at the 'Upload File from a URL' field when you are posting. (easier if you follow along on these instructions as you actually are trying to do it)
On a Mac
, two-fingered click on the image on the gallery page and select 'Copy Image Address' from the menu that opens. That will put the image URL on your clipboard -- just paste that URL at the 'Upload File from a URL' field when you post.
Do this a few times and the $20 annual contributing member cost might seem reasonable. But it does get more automatic and moves pretty fast once you understand it enough to set up efficient work patterns, working in multiple tabs, etc.
One note about pushing back the date your attachment quota gets full -- try to avoid attaching the allowed 1600 pixel maximum size images. 1000 pixels or 1200 pixels shows up just fine on most peoples' computers; eg, 750 x 1000 pixels or 900 x 1200 pixels if your camera aspect ratio is 3:4. Different number apply to 2:3 aspect ratio cameras but most editing software allows proportionate downsizing so you don't have to do the math every time. Paint on a PC has one of the quickest accessible resize functions.
And don't forget -- click 'Save' on your resize and you will overwrite (destroy) your original image file! Pffft, it's gone!! Only click 'Save As..' -- I 'save as' to my desktop so I can find it easily for posting and later deleting.