LAMMPS can produce on-the-fly JPG or PNG snapshot images via its dump image command. However for high-quality, interactive visualization, you need tools like those discussed on this page.
These are high-quality visualization packages we have used and recommend. LAMMPS can either write output files directly in an input format recognized by these programs (see the dump command), or contains auxiliary tools to convert to the needed format:
Our group has also written and released a toolkit called Pizza.py which provides tools for doing LAMMPS pre- and post-processing, and which includes a simple OpenGL-based visualization tool called gl. Pizza.py is written in Python, is available for download from this page. It includes Python wrappers that drive the Raster3d and RasMol packages listed above. It also includes tools that convert LAMMPS output into input files readable by VMD and AtomEye.
These are visualization tools we know less about, but which have features that may be attractive to LAMMPS users. Some details are given below:
Guido Germano (Philipps-Universitaet Marburg) sent a link to his freely-available package QMGA which does OpenGL rendering of non-spherical (and spherical) objects. This could be useful for visualization of aspherical particles simulated with LAMMPS.
Erik Abrahamsson (U British Columbia) sent a link to his group's BioVEC visualization package. It allows for easy visualization of ellipsoidal particles. "The BioVEC program is written in C++, uses the OpenGL API for rendering, and is open source. It is lightweight, allows for user-defined settings for texture, and runs on either Windows or Linux platforms."
VisIt is a general purpose visualization package developed at LLNL and has support for LAMMPS dump file formats as explained here.
This page lists third-party software that wraps LAMMPS with GUI and analysis capability. This includes visualization of LAMMPS output.