import numpy as np

plot_image = image_list[1]
for i in range(20):
    plot_image = np.concatenate((plot_image, image_list[i+1]), axis=1)

plt.figure(figsize = (15,15))
plt.imshow(plot_image, cmap = 'gray');

import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid1 import ImageGrid
import numpy as np

fig = plt.figure(1)
grid = ImageGrid(fig, 111,  # similar to subplot(111)
                 nrows_ncols=(2, 2),  # creates 2x2 grid of axes
                 axes_pad=0,  # pad between axes in inch.
                 )

for i in range(4):
    grid[i].imshow(np.random.random((10, 10)))  # The AxesGrid object work as a list of axes.
    grid[i].axis('off')
    grid[i].set_xticks([])
    grid[i].set_yticks([])