Since 1992 an asteroid belt has been discovered farther than Neptune. The biggest bodies are similar to Pluto's size, and they question its planetary status.

Pluto, formerly the nine planet, is the second largest Kuiper Belt object. What is sure is that it's very small and far away, and in most images it looks insignificant.

Eris, formerly the "tenth planet", is an object the discovery of which, has changed the classification of the outer Solar System. Physically Eris is similar to Pluto, and it's even a little bigger.

More info on Eris is found on Wikipedia.

Sedna is an asteroid farther than Kuiper's belt. Discovered in 2003 it has a diameter of 1600 km and an extremely long orbita, which takes 12000 years to complete.

Quaoar is an asteroid of the Kuiper's belt. When it was discovered in 2002, it was the biggest, with a diameterof about 1200 km.

Makemake (2005 FY9) and Haumea (2003EL61) are the brightest asteroids of Kuiper's belt, after Pluto. They have a diameter of about 1600 km, but the latter is extremely oblonged.

Pluto, high resolution imaging

A typical image of Pluto is starlike, but with longer focal lenghts is teoretically possible to show a oblong image due to the satellite Charon. Sadly, the long exposure times to show the planet (5-8s) limit the resolution because of the growth of turbulence.
Some double star was imaged for testing the resolution of the setup, showing the possibility to detect Charon with shorter times of exposure (0.1s)

Pluto, high resolution imaging

With intermedium focal lenghts, the image of the false disk of Pluto is the reflect the seeing of the night (~2").

Pluto on film

Eris, (2003 UB313), the largest dwarf planet

The transneptunian Sedna

The transneptunian QUAOAR

The transneptunian Makemake (2005 FY9)

The transneptunian Haumea (2003EL61)