In Tibia we can see 4 different sizes of items - 32x32, 32x64, 64x32 and 64x64.
Check the look of tapestries:
You can notice, that each tapestry has 3 stages.
1) when item is lying on the floor - it is in 32x32 size.
2) when item is hanged on the northern wall - it is in 64x32 size.
3) when item is hanged on the western wall - it is in 32x64 size.
32x32px is reserved rather for items (ofc there are exceptions), while size 64x64px is most popular for objects, big monsters.
During fansite item contests it is possible to create item which we can hang on the wall in sizes presented above.