If I understand correctly you have used LibreOffice Draw to create svg file type and you would like to use this svg file in your own created application.
As far as I know in this case you are not obligated to make note in your program or license the file in any way. This is not a LibreOffice license problem. The LibreOffice license problem would be if you took SOURCE CODE of the LibreOffice program and release this program code under your terms - you would need to apply to the LibreOffice terms. Because you are (as I understand) not changing any source code from LibreOffice you are not effected by this LibreOffice license.
The main question in my humble opinion, is how did you get PNG images? Are this images somehow licensed? If yes, then you need to consult with the PNG images author, PNG image license owner.
In my humble opinion this your problem (converting PNG images to svg) has absolutely nothing to do with the LibreOffice license. Except, Yes sure, if the owner of PNG images is some author of LibreOffice program… but in this case you need to provide more info.