I've just used this in Rails 4.1 as well with Galleria version 1.3.5. Copy the files from the main galleria folder into the various parts. Note that I'm using the classic/default (free) theme.
# app/assets/images
classic-loader.gif
classic-map.png
# app/assets/javascripts
galleria-1.3.5.js
galleria.classic.js
# app/assets/stylesheets (rename with .scss extension)
galleria.classic.css.scss
Open up galleria.classic.js
and edit the line css: '...'
to be css: false
(around line 17 if you don't alter the code).
That's all I had to do in order to get it working with Rails 4. I played around with placing the files in the vendor/assets
folders, but that became a nightmare fairly quickly. I found the above solution to be the simplest/cleanest.
Update: 2016-02-02
I'm still using this same setup with a Ruby 2.2.3, Rails 4.2.4, Galleria 1.4.2 setup.
Make sure in your galleria.classic.scss
stylesheet you use the image-url("classic-map.png")
helpers. No problems with this current setup.