From LightWiki

Using LightWave 3D as an animation translator

The tutorial below was written for LightWave [8] originally, but also works with LightWave v9, only the screenshots for the Render Options have been changed.

We all know that you can only render out image sequences if you use Screamernet to render, and outputting frames is the way to go for long complicated renders anyway, since if your machine crashes partway through a render you can simply restart at the last frame rendered, rather than having to do the whole lot once more. However, many people think that an external application is then required to put those single images together as an animation... Not so!

Start LightWave's Image editor (F6) and choose the first image in your sequence. Once loaded, select Sequence from the Image Type drop-down menu.
Now open the Compositing window (Ctrl F7) and use this sequence as your Background Image. Take a note of the resolution.
This next step is optional. If you would like to see your sequence in Layout, and be able to scrub through it using the timeline, open your Display Options panel (d) and down at the bottom you can change the Camera View Background to Background Image.
Next up, in Camera Properties, select the same resolution for your animation, otherwise it will be blurred up to a higher resolution or shrunk lower (not really possible in this example!). You can turn off anti-aliasing since it's not needed. Any anti-aliasing should have been done when you first rendered the sequence.
Lastly, in Render Options, set your desired animation format. Note you can also use LightWave to render out an image sequence in a different format to that you already have if you have no batch converter for images.

You'll note also that although my animation sequence consists of 80 images, I can truncate it here by only rendering the first 60. If you can the render number set higher than the number of images, the animation will hold on the last frame depending on the options set in the Image Editor window.