In this link you will find an useful guide to install DOM with Image_gallery and other nice modules:
When you dev/build Image_gallery module, you recieved a fatal error, 'ImageUploadField' class was not found. My solution was try with others 2 Image_gallery versions that i tried in SS v2.3.2 and v2.3.5, the results were the same, with some error in some page of the CMS. Then i decided to try other versions of DOM.
Finally i've found what DOM version works fine with Image_gallery module. It was the one used in ss v2.3.5.
Here is the link where you can download the module :