Great news! You have control over the way that the images you upload are sorted. 

To set the upload order of your images, click on your username in the top right corner and select User Settings from the drop down menu. 
Next, choose the Albums tab on the User Settings page. 

From this page you can change the way that all new uploads and current albums are sorted. 

The drop down menu provides reveals three sort options:
Newest First: This option will sort your media by the date in the metadata attached to the file. Images without metadata are sorted by upload date. 
Oldest First:  Display your older images first. This comes in handy when you want photos sorted in chronological order. 
Alphabetical Order: Exactly what it sounds like! Sort your images in numerical and alphabetical order by file name. 

Check the box below sort options to sort all existing albums the same way.  Remember to save after you make any change.