[help needed] Can someone explain property.layers of the style manager? [pls read description]

I would like to code the entire background layers property but this time using 'background' instead of background-image so it doesn't mess up the gradient but unfortunately can't bring background-position, background-size, etc to work.

        var property = editor.StyleManager.addProperty('decorations',{
          name: 'Background Image',
          property: 'background',
          type: 'stack',
          properties:[
            {
              name:'Background',
              functionName:'url',
              type:'file'
            },{
              name: 'Background Position',
              property: 'background-position',
              type: 'select',
              list: [{
                value: 'left top',
                name: 'left top',
               },{
                value: 'left center',
                name: 'left center',
               },{
                value: 'left bottom',
                name: 'left bottom',
               },{
                value: 'right top',
                name: 'right top',
               },{
                value: 'right center',
                name: 'right center',
               },{
                value: 'right bottom',
                name: 'right bottom',
               },{
                value: 'center top',
                name: 'center top',
               },{
                value: 'center center',
                name: 'center center',
               },{
                value: 'center bottom',
                name: 'center bottom',
               }],
            },{
              name: 'Background Repeat',
              property: 'background-repeat',
              type: 'select',
              list: [{
                value: 'repeat',
                name: 'repeat',
               },{
                value: 'repeat-x',
                name: 'repeat-x',
               },{
                value: 'repeat-y',
                name: 'repeat-y',
               },{
                value: 'no-repeat',
                name: 'no-repeat',
               }],
            },{
              name: 'Background Attachment',
              property: 'background-attachment',
              type: 'select',
              list: [{
                value: 'scroll',
                name: 'scroll',
               },{
                value: 'fixed',
                name: 'fixed',
               },{
                value: 'local',
                name: 'local',
               }],
            }
          ]
        });

but the result is something like this -> background: url(../assets/347f05a7ef54b27632187b38a1ddfe65) left top repeat; }