I noticed that the battery percentage of pir sensors is displayed instead of the tile template name (by unchecking the "hide tile template names" option) while on contact sensors the percentage is correctly displayed in a separate div (tile-tertiary).
Is it possible to solve the problem or does it depend on something else?
I'm not doubting your experience.... But some screenshots will likely help capture your experience more accurately.
Could it be that it's reserved for temperature?
Here's mine:
I don't know. Here is what a contact sensor I have looks like.
The zigbee sensors usually have temperature.
I (or someone else) would need to look at the HTML involved... but I expect the "hiding" might include unwanted elements like you are observing.. There will likely be options available to avoid this, but we will need to look at it some more (hopefully others will chime in ahead of me 
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@velvetfoot - The next steps I would suggest, if you want to, would be to look at the developer tools (F12 in Chrome) to understand the Elements presented and their classes.
This is what I get when I unhide the template names.
It makes my skinny other tiles look bad.
The problem I think is related to positioning rather than the hiding option. The value should fall within a span of the tile-tertiary div.
Like this contact sensor:
instead in the motion sensor template it ends up in the tile-secondary div without a defined class.
Sounds like you are on the way to some custom CSS to achieve what you need, along with a built-in fix. I can provide some more detail on the Custom CSS later if you need it (if no-one else chimes in before me).
I've already customized it the way I want it to be, but there is a need for the fix to maintain a general consistency.
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