I started with Darshak Parikh's suggestion.And realised I have to replace the symbolic links (symlinks) in the /usr/share/icons/<your-icon-theme>/mimes/<your icon size> folder. In my case <your-icon-theme> was the default Ubuntu Unity theme Humanity and as for <your icon size> I just replaced sizes 163248128256.
Here is a part of the code which can help you do the same, You would consequently have to replace 16 with 32, 48, 128, 256 to fit your resolution I guess. To be honest I didn't tried just replacing the 16 size folder, I did it all and then a computer restart ( -- I didn't knew which service to restart)
wget -O ~/Dowloads/ "http://svgicons.o7a.net/unofficial/OOoBase.svg"wget -O ~/Dowloads/ "http://svgicons.o7a.net/unofficial/OOoCalc.svg"wget -O ~/Dowloads/ "http://svgicons.o7a.net/unofficial/OOoDraw.svg"wget -O ~/Dowloads/ "http://svgicons.o7a.net/unofficial/OOoFormula.svg"wget -O ~/Dowloads/ "http://svgicons.o7a.net/unofficial/OOoImpress.svg"wget -O ~/Dowloads/ "http://svgicons.o7a.net/unofficial/OOoWriter.svg"sudo cp ~/Downloads/OOoBase.svg /usr/share/icons/Humanity/mimes/48/OOoBase.svgsudo cp ~/Downloads/OOoCalc.svg /usr/share/icons/Humanity/mimes/48/OOoCalc.svgsudo cp ~/Downloads/OOoDraw.svg /usr/share/icons/Humanity/mimes/48/OOoDraw.svgsudo cp ~/Downloads/OOoFormula.svg /usr/share/icons/Humanity/mimes/48/OOoFormula.svgsudo cp ~/Downloads/OOoImpress.svg /usr/share/icons/Humanity/mimes/48/OOoImpress.svgsudo cp ~/Downloads/OOoWriter.svg /usr/share/icons/Humanity/mimes/48/OOoWriter.svgsudo cp /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.presentation.svg ~/Downloads/presentation-16.svgsudo rm /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.presentation.svg sudo ln -s /usr/share/icons/Humanity/mimes/48/OOoImpress.svg /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.presentation.svg sudo cp /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.spreadsheet.svg ~/Downloads/spreadsheet-16.svgsudo rm /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.spreadsheet.svg sudo ln -s /usr/share/icons/Humanity/mimes/48/OOoCalc.svg /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.spreadsheet.svg sudo cp /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.database.svg ~/Downloads/database-16.svgsudo rm /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.database.svg sudo ln -s /usr/share/icons/Humanity/mimes/48/OOoBase.svg /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.database.svgsudo cp /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.drawing.svg ~/Downloads/drawing-16.svgsudo rm /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.drawing.svg sudo ln -s /usr/share/icons/Humanity/mimes/48/OOoDraw.svg /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.drawing.svgsudo cp /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.formula.svg ~/Downloads/formula-16.svgsudo rm /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.formula.svg sudo ln -s /usr/share/icons/Humanity/mimes/48/OOoMath.svg /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.formula.svgsudo cp /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.text.svg ~/Downloads/text-16.svgsudo rm /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.text.svg sudo ln -s /usr/share/icons/Humanity/mimes/48/OOoMath.svg /usr/share/icons/Humanity/mimes/16/application-vnd.oasis.opendocument.text.svg