AttachmentViewer and Image Limitations

There are some limitations on the size of the attachments and images that you can include as part of the Mobile Workflow message.

These limitations vary by platform.
Platform Size Limit
BlackBerry 5.0 and BlackBerry 6.0 On BlackBerry 5.0, the maximum size of a JavaScript variable is 500KB and on BlackBerry 6.0, the maximum size is 2MB, which means that the maximum size of attachment included as part of a Mobile Workflow message must be less than that. Keep in mind that you have to include the rest of the Mobile Workflow message, in addition to the attachment contents, and also include allowances for an increase in the size of the attachment when it is Base64-encoded to allow it to be included in the XML message.
Windows Mobile The maximum size of a JavaScript variable for Windows Mobile is 2MB, which allows for more memory. Warning messages are shown if the script continues for a long time, which can cause the memory to run out.
iOS Large attachments can produce longer processing times.
Android Large attachments can produce longer processing times. There is a 1MB limit for attachments on Android devices.
Note:

When accessing very large binary (image) data in the mobile business object associated with the mobile workflow, ensure that the attribute set in the mobile business object is a BigBinary datatype, rather than Binary.

Related reference
SUPStorage.js