I found this in the Tile backgrounds:
ResizeIconByPercent = 80;
OffsetIconByPercentX = 50;
OffsetIconByPercentY = 00;
But I don't know how to implement it in my current background.
There is currently no universal setting for this, it must be done per background. That being said, open the folder for the background you'd like smaller icons for. If it's not already done, do the following:
1. Add a blank .png image to the folder. Name that image "blank.png".
2. Open the .ini file for the background whose icons you want to edit. Add these lines to the top of the code (under the name):
Image = blank.png
ResizeIconByPercent = 75
OffsetIconByPercentX = 50
OffsetIconByPercentY = 50
3. Save the .ini file then apply the background through your ObjectDock settings.
I already program these settings into almost every background I create. I personally prefer slightly smaller icons than default, and this also naturally creates more spacing between them.
I would not recommend manually changing your icon image files unless you saved a back up first.