All the different buttons like play, pause, fullscreen, info, tags, download, etc is altogether referred as button set here. The user visiting the website may or may not choose to set it as per their preference. Button-sets are located in root_dir > phpix-imports > buttons > button-set-directory. button-set-directory is thefolder where your button set files will be kept. There is only one css file named style.css for styling.
Method 1 : Button sets can be creating just by replacing the original svg files in svg directory with new svg files of your choice. This method is good for people who do not posses knowledge of css.
Method 2 : People with knowledge of css can do advanced theming by restyling the css file and using svg files, png files, unicodes or iconic font files. All you have to keep in mind that you are going to restyle the predifined css classes. For easy start, just copy any button set folder to root_dir > phpix-imports > buttons > your-button-set-directory, edit the style.css file as you need.
Now, you may want to see your button-set in action. Login to admin and goto options tab. You should see your button-set listed there. Check the checkbox and press save changes button. Now your button-set would be listed at gallery page. When giving name to a button-set folder, use small letters, numbers, hyphen and underscore.
That's it friends. End of this story!