It is a common issue in Magento. After uploading images from back end, the images are shown in back end, but are not displayed on the front end. To solve follow the below steps. Any one of them might solve the issue for you, or even you might need to apply all. Try your luck
1. In back end go to System -> Cache Management. Click all check boxes. Choose ‘Refresh’ option from ‘All Cache’ drop down. Click ‘Save Cache Settings’. Once the page reloads select ‘Disable’ from drop down and again press ‘Save Cache Settings’.
2. On the same page you will find a button ‘Clear’ beside ‘Images Cache’. Click it.
3. Go to Catalog -> Manage Products. Click the specific product. Go to ‘Images’ tab. Beside the image there will be 3 radio buttons (Base Image, Small Image, Thumbnail). See if the required radio is selected or not. Also check if Exclude is checked or not. If checked uncheck it and save product.
4. Upload another image. Assign all radio to that image. Save the product. Then reassign the required radio options to the actual image and save again.
And yes also clear your browser cache. I hope by now the image is showing in front end. If not just add a comment.