I used the following code in Win 10 PowerShell to create the above images.

gmic.exe `
  input 200,50,1,3 `
  rand 0,255 `
  +resize 1000,250 `
  +blur[-1] 3 `
  output gmic_rand.png `
  output gmic_rand.jpg

G'MIC
RAND

• gmic.exe
• This is the program I am calling.
• input 200,50,1,3
• Creates a blank 200x50 blank image...
  • Of the standard sort.
• rand requires a template from which to work.
• rand 0,255
• The G'MIC command which fills an image with random values.
• The range of these particular values is 0-255 inclusive.
  • Passing the same value for both parameters does not cause rand to choke.
• For tiling patterns, fill may be more appropriate.
• And for yet other applications, noise (and all its variations) may be just the ticket.
• +resize 1000,250
• The plus in front means add the output of this command to the image list.
  • Without it, the image (array, or whatever you want to call the pseudo-image at this point) is altered in place.
• I am impressed with the hardiness of these commands.
• I have not found a way to make resize choke...
  • Not yet.
  • Maybe negative numbers would work.
• gmic help resize is the command to use to discover the available interpolation methods.
  • I'm not that picky.
• +blur[-1] 3
• +: adds an image to the stack.
  • Thus, the transformation is not done in place.
• blur: this be the command in question.
  • Guess what it does?
  • If stumped, might I recommend gmic help blur.
• [-1]: applies the effect to the last image on the stack.
  • No [-1] (i.e. +blur 3) and the blur would be applied to the stack...
    • Outputting two additional images (+1 additional image per image already on the stack) rather than the one.
• 3: The final number is the size of the disk...
  • Truthfully, I haven't got the slightest idea how 'the disk' is measured...
    • Or even if the fine folks (the very fine folks, indeed), who wrote G'MIC think in terms of disks.
• output gmic_rand.png
output gmic_rand.jpg
• This is sheer awesomeness!
• The stack is exported twice!
• Also, I don't have to do anything extra to export the entire stack.
• The output images are automatically renamed.
  • gmic_rand_000000.png to gmic_rand_000002.png
  • gmic_rand_000000.jpg to gmic_rand_000002.jpg
• G'MIC does not care about existing files.
  • Name collisions are silently ignored.
  • Existing files are happily overwritten.

Similar Commands

If rand doesn't quite do the trick, I would look at fill (especially for any tiling needs) or the various noise commands (noise, noise_hurl, noise_perlin, and/or noise_poissondisk) if I were interested in some form of static.