langify is currently able to translate static images in your theme and images in the descriptions of your products, pages, blog posts, etc.
I am working on implementing the translation of product images in langify.
Until this feature is ready you can workaround the issue by following this tutorial.
Open the page with the image that you want to translate.
Now you have to search for the url of the image. Using the Chrome Development Tools makes this an easy task.
Copy the url (in this example it is //cdn.shopify.com/s/files/1/0422/0317/products/white-t-shirt_en_1024x1024.jpg?v=1401542248) and create a new "custom content" in langify by clicking "Add new custom content" in the "Translations / Custom" section (http://langify-app.com/customs).
Paste in the url of the image that you have copied in step 3.
Click "Create" and navigate to the "Settings / Files" section of your shopify backend.
Click "Upload files" and select the translated image.
Copy the url (only the part after the http:) that shopify has uploaded the image to (in this case it is //cdn.shopify.com/s/files/1/0422/0317/files/white-t-shirt_de.jpg?922) and navigate back to the "Translations / Custom" section in langify.
Click the content that you have created in step 5.
Translate your image url by pasting in the url that you have copied in step 7 and click "Save".