What format are the screenshots in? Do you upload directly from your documents folder, or do you use Photobucker or Imageshack? Do you have any problems with uploading the screenshots?
I tried to upload them directly to here, the photos failed to upload. I tried uploading the .jpgs to Photobucket, it said failure due to invalid file type. :\ Trying to upload one converted to .png, it’s kinda stuck on the halfway mark due to this internet.
I never upload from the DA screenshots folder - in part because I’m an organizational basket case with my screenshots. Have you tried moving them?
Depending on the size of your game screen (it caps to full resolution), your problem might be that your game is generating incredibly high resolution files. My suggestion would be to open the images in a file editor (if you don’t have something like Adobe Elements, try GIMP, which is a free and very functional version of Photoshop), resize, and save to another location. You could also try just moving them altogether.
Tumblr is pretty obnoxious about images files, sometimes, too. Though this shouldn’t be your issue, if the image is in a CMYK color mode, it won’t upload. Tumblr images should always be uploaded in RGB.
I hope that helps!