you mean there are several TVs that offer 1024x768? these are 4:3 data displays... not officially supported by Apple TV, although it wold work. the last plasma's I saw that have this native resolution were made by Hitachi and Pioneer, back in 1999 or 2000.... manufacturers haven't been making too many sets since then. of course there are lots of smaller LCDs - sort of rebadged computer monitors with this resolution.
any 1080i or 1080p set on the market now can also input 720p, 480p, and 480i (for the US market... substitute other rates for PAL/SECAM models) - so you are perfectly backwards compatible with lower rates.
There are a number of panels (Plasma and LCD) which have a 16:9 shaped screen - but the pixel aspect ratio is 4:3.
This is more of a problem for the Mac Mini than the Apple TV.
If the Mac Mini sees a pixel format of 4:3 - it assumes that the screen is 4:3 and produces a image which is then distorted when displayed on the 16:9 TV.
As I understand it, the Apple TV always assumes a 16:9 screen aspect ratio, regardless of the pixel resolution.