The time taken to upload photos is dependant on the speed of your internet connection. For example, uploading 10 images on a connection with a 5 megabit upload speed will take around 96 seconds. On a 1 megabit connection, this increases to 480 seconds - 8 minutes.
If you are having trouble uploading a batch of images, please try uploading in smaller batches.
Note that this does not apply to the mobile app - photos are compressed before being sent (typically 10% of original size), upload far more quickly and upload in the background.