Embedded image data inside a JSON string.

Interesting. ESTK crashes when it doesn't like the image string.

So, I took your javascript unicode-escaped image string and ran it through:

Escape for JSON and Javascript online tool‌

Then validated the below test JSON here:

JSONLint PRO - The JSON Validator

[
    {
        "image": "\\u0089PNG\\r\\n\\x1A\\n\\x00\\x00\\x00\\rIHDR\\x00\\x00\\x00F\\x00\\x00\\x00\\x1E\\b\\x02\\x00\\x00\\x00\\x1E\\u0091\\u00FFI\\x00\\x00\\x00\\x19tEXtSoftware\\x00Adobe ImageReadyq\\u00C9e<\\x00\\x00\\x03\\u0099IDATx\\u00DA\\u00EC\\u0098\\u00CDK\\x14a\\x1C\\u00C7\\u009DZ\\u00EC\\u00D0\\u00AE\\x07\\x13\\u00D4\\u00C4\\u00C2\\u0097\\u00D8,\\u00D8\\x12\\u0094\\u00A0\\b\\u00A2 \\n\\x02o\\u00DD:t\\u00EC\\u00D6\\u00BDK\\u00E7\\u00AE]\\u00FA\\x03\\u00BAu\\bO\\u0082\\u0081\\u0087\\u00C4 \\x14,\\u0083PR\\u00935S!]h\\u00D7C\\u00B3\\u0097>\\u00E3\\u00D7~>\\u00CC\\u00AC\\u00B3\\u00B9\\u00BB\\u00A2\\u00C8>\\f\\x0F\\u00CF<\\u00FB{\\x7F\\u009F\\u00F5\\u00DE\\u008F\\u00CE4\\x1C\\u00AFu\\u00A2\\u00E1\\u00D8\\u00AD\\u00BAJu\\u0095\\u008E\\u008AJk\\u00EB?\\u00E7\\x17\\u00E6\\u008E\\u009B\\u0097\\n[\\u00F9Z1\\u00C0@\\u009Ff\\u00A6\\u00D8c`\\x00\\u00D8/\\u00D9\\x18\\u0094DT\\u0082o\\x0B\\u00B3\\u0086\\u00B6\\u00BA\\u00B6\\u00D2\\u00DE\\u00D6\\u00A1\\u00D7\\u00E4\\u00E9T[\\u00EB\\u00D9\\u00F9\\u00C5\\x1D\\x07^\\u00CD\\f\\u0084\\u00A8\\u00F7v\\u00A7\\u0093\\u00C9\\u0094\\u00CE\\u00F8Yv\\u0081Z\\x7Ff\\u0090\\u00BDP\\u00C8\\u009B\\u00A5\\f\\u00D7\\u00E5\\b\\u00FD\\u00DE\\u009E\\u00B4K\\u00D0n\\u00C0\\x15_ndq\\u00A1\\u00B8\\x1Cm\\u009D|\\u00FC\\u00E8\\u0089\\u00FB\\x0E\\u00C4\\u00F9\\u00CE\\u00AE\\\\n\\x03\\u00E9y.\\u00F4\\\\\\x1C\\u00FF0v\\u00E7\\u00D6=\\u00CE~\\u00D1\\u00FF85q\\u00F3\\u00FAm\\u00CE\\u0090\\u00CE./57\\u00B7Hm]~\\u009D\\u00FD\\u00C2.:\\u00D9\\x1FK\\u00C8\\u00CD\\u00EB\\u0099\\u00E6\\x16\\u00DF\\u00F7\\u00A13=3\\x19\\u00C25\\u008E\\u00C5\\u00A2\\x0F\\u00B0n \\b\\u00C0\\u00A5\\u00BE\\u008C8\\\"=\\x00P\\x165n6s\\x1B\\u009C\\u0085\\u00D2\\u00D8x\\u00AA\\u0092\\u00F2\\u00804:@q\\u00D7c\\u00C9\\u0094L\\x0E{\\u00D9\\u00C9u/+_\\u00F8m\\u0096f\\u00C7.\\u00E8\\x13\\u00C2-\\u00B9 \\\"\\u00CF\\u0088\\u00A3\\\"\\u00D6\\u00A8\\u00C9\\\"\\u00F1\\x02'\\u00AAL\\x15\\u00E4Km5aZ\\u00B9T\\u0097(@\\u00A8\\u00B0\\u00A7\\u0092M\\n\\u00B3\\u00D5\\u00F5\\x15\\u008BX\\u00D3\\u00B3D\\x0E\\x17\\u00F2\\u00FC\\u00E4\\u00E6\\u0089\\u00DC\\u00AE`\\x11\\u0080\\u0099f\\x07>\\x12x\\u0089\\u00EA\\u00B3\\u00DF\\x12C^\\\"\\u008B\\u00D0\\u0084\\u00FCq\\u0099q\\u00E3\\u00E6\\u00CF^\\u00C9\\u008D\\u00DA\\x04B\\bR\\u00BE2M\\\\\\u0087\\x03\\u00EF\\x02\\u00C7\\x05\\x1E\\u00E9af0\\u00A7\\u00EFu6\\u00DD\\x14$\\x04\\x15?\\u00C1\\x18i\\u00EC!\\u008FM\\u008Dh\\u0087\\u00B0\\x00\\u0093\\x03\\u00ED\\f\\x11yi\\u00FA\\u00F3\\u00A4\\u00F1mo\\u00ED\\u0088\\u00B7\\u00B2\\x17\\x1A[\\u00AD\\u00B6\\u00B8\\u009C\\u00940%\\u00CF\\u00C4\\u00BDdU\\u0094\\u0083\\u008B\\u00F4!\\u00E3\\u0089\\u00A6\\u00EE\\x05iUd\\u00D7?\\u00DB\\x15RXf\\x1D+hv\\x13\\u00AA\\u0081%Iy\\x071\\u0089\\u008F\\u008C\\x0E\\u00DF\\u00BF;d\\u00AF\\x18;\\x14\\u0087\\x07\\u00BA\\u00CA\\u00AB$\\x0B\\u0099y*h\\u0085%\\u00BB\\u00C7\\u00A1\\u00CDxA\\x7F,\\x04\\u00F1\\u00F0\\u00F2\\u00D5\\u008B}\\u00D1\\x05\\u00C5\\u009E\\u00FF\\u00D7\\u00E7\\u00D9\\u00F3\\u00A7e\\u00ED[\\u0095\\u0097\\u00E4\\x1Fl\\x1C\\u00EC=\\u00E9P\\u00F8\\u00CAu\\u00AA\\x07\\u00FC\\x14\\u00F5\\u00A1\\u00CA@\\u0090c\\u00FFT2\\u0082\\u0096\\u008D\\u00C18\\u00B20\\u00C7\\u00AB\\u00E5\\u00AD\\x11\\u00D7Y\\u009DW\\u00DCU\\u00E2\\u00CA\\u00C6K\\u009C\\u0097\\u00A0H]\\u0096\\x1A\\u00F0\\u00A0\\u00FD+}\\u00DF\\u00BC}\\u00BD#\\u00CD\\u00E2\\u00DC\\u00C8\\u00BBa\\u00E3\\x1D\\n<)/`%\\u0098\\u00BC\\u00A7\\u00B1\\x18\\u00C9T\\x15\\u00A5CP\\x1E\\u00B6[\\u0099)\\u00CF\\x19\\\\\\u00F4\\x07\\u0080\\u00B3\\u00AC\\u0080<\\u00D1zPf \\n-\\u009B;\\u0090\\u00FE\\u00DA\\u00C0\\r\\u009B\\u00984\\u00FB\\u00F0l\\u00E6~]\\u00EE\\u00CB\\u00F0\\n3\\x0E\\u00AE\\u0087\\u00CFuv\\u0081\\u00E8y\\u009E\\\\\\u00C1\\u00AF\\x1Ay\\u0098\\u00AA\\u00FC\\u00E2\\x1F\\u00BA'\\u00C4\\u00E51$\\u00E6\\u00A6\\u00FF\\u00CA 7\\u0092\\u0098=\\u00BB\\u00FC}\\u00E8\\u00C1C(\\u00F0\\u00C0\\x11\\u00E5\\u0099\\u0092\\x00\\u0080l\\u00ED\\u00A7\\u0087P\\x0F\\u0095\\x04\\b\\x17\\u00AD{\\u00F4M\\u0089\\u00A8Q\\u00CD&,\\u00B3\\u00B4.\\u00B9\\u0089\\u00C6\\u0092\\r_\\u0087\\u00F3\\t\\u00E8&\\u008C\\u00A2\\x0E\\u00DFR\\u00C7\\u00D9\\u00E9\\u0092\\u00A1\\u009C\\u008EJ\\u00BF\\u00AFZZ\\u00B2YW\\u00AB\\x12\\\"\\u0096\\rhe3\\u008B\\u00E1\\u0085\\u00B3;\\x1F(\\u00CB\\u00CBr\\u00B1\\t&\\u00CA1\\u00FEs.\\x11o\\f2\\u0084\\u00E9&\\b\\u008C\\u00EE\\u00B4\\u008D\\u00A1\\u0096\\u00E5\\u00FC\\u00BAW\\u00CBr\\u0085VQq?\\x04\\u0083I\\u00C2!n\\x15\\u00C2\\u00BD!\\u00F0\\u00A2\\x1FN\\u00F6\\u00F5QU\\u00AB=\\u00AC\\u00A5\\u00E8\\u00AD\\x001qd\\u00F5\\x19\\u009F\\x18\\u00ABl\\u00F2\\u00F0\\u00EA\\u00FF\\u00B6\\u00D6U\\u00AA\\u00ABT\\u0093\\u00F5W\\u0080\\x01\\x00H@\\u00A4W\\u009F\\u008F\\u00E9\\u009D\\x00\\x00\\x00\\x00IEND\\u00AEB`\\u0082"
    }
]

Validates as JSON. You'd just need to unescape before calling it in a dialog window.

Not sure if that's headed in the right direction, but that's probably the route I would head.