<p>I managed to tear my build plate trying to get some very stubborn plastic off it.</p>

<p><a href="https://i.stack.imgur.com/fDqad.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fDqad.jpg" alt="Torn build plate"></a></p>

<p>I'll need to buy a new one, what characteristics are important for me to ensure it's compatable with my printer?</p>

<p>I can think of:</p>

<ol>
<li>Dimensions</li>
<li>Power requirements</li>
<li>Connector types</li>
<li>That my printer moves the plate in the z axis (?)</li>
</ol>

<hr>

<p><em>NB</em>  I'm so new at this I didn't realise that this was just a sticker on the plate, so I just need to replace this sticker.  However, as a question, I'm still curious as there's a good chance I will break it at some point.</p>

If your printer's heated bed still works, but the sticker has been ripped in some places:
You can try and remove the rest of the sticker, clean the metal plate under the sticker (perhaps with isopropyl alcohol) and then apply a new sticker once there is no adhesive remaining on the heated bed.
You can remove the sticker with the method above, but instead of replacing it with a new sticker, you can buy a PEI sheet and cut it to size if required (read more about PEI
here
) and then stick it to the metal plate.
Personally, I would recommend the latter option, since PEI is low maintenance and the prints automatically pop off the sheet once it cools down, however just make sure not to print PETG on it, since it sticks too much.
On the other hand, if your entire heated bed is broken, the best-case scenario is to look for a heated bed that was designed specifically for your printer. Especially since your printer's heated bed has 3 mounting screws instead of 4.
If you somehow have a solution for mounting a heated bed with 4 mounting screws on a printer that uses 3, the things you need to watch out for are the heated bed's operating voltage (it should be 24v) and the dimensions must be the same. If the wires are not provided with the heated bed, make sure to get wires that have high enough gauge so that it is able to handle the high currents that the heated bed will need.