There are size limits to the Gallery. Your photo's are way too big for a monitor. They should be less than 100kB each which is plenty large enough for any monitor.
If you just upload 500 KB photos, you will run out of space in a hurry, and the photo when at full size will be much wider than a normal monitor, so everyone viewing it will have to scroll back and forth on the ultra wide pic - which is a PITA.
Read this thread
Tips on Picture Uploads and Image Sizes
Here is a 45KB sized pic ... just a little too small so the detail is not that good. 80KB or 100KB would be better for this pic.
and a 200 KB sized pic ... more that enough detail for a monitor.
I normally take all my photo's in the 500 KB size for an average day. If its a really nice day and I find some good background, I change the camera shot selection to 2 or 4 MB. Then I can print an 8 by 10 and it looks good.
Then I use the XP Power Toy re-sizer program to resize any of the pics down to about 80 KB that I want to load to CC or any other pic storage site.