Painting the large siding area of the house pixel by pixel could get a little tedious, so let's create our own pattern tile.
Open new image, 24x24 pixels with transparent background.
Using the darkest gray from swatch, paint a 1 pixel horizontal line.
Using the middle gray, paint another line under the dark gray line.
Using the lightest gray paint 1 more line.
On the next line, paint 1 pixel the lightest gray, then 1 pixel white, repeat for a check pattern all the way across.
Paint 2 more rows all white for a total of 6 lines in the pattern.
Copy those 6 lines and paste as new selection underneath the top 6 lines.
Paste again, 2 more times to fill up the 24x24 pattern.
Return to Rose Cottage, HOUSE layer. Load the HOUSE selection from alpha channel.
Choose 'Pattern' tab on the Materials palette. Locate the siding pattern you just made. Angle should be 0 and Scale should be 100. Texture should be UNchecked.
Flood fill each section of the house front with this pattern.
Return to the pattern tile and change it to a brick pattern for chimney. Make these changes to pattern on a separate layer if you want to keep both patterns.
In the top left corner, paint a 6 pixel tall vertical dark gray line connecting the dark gray lines of the existing pattern. Move over 12 pixels and paint another. Repeat for each row, alternating in a brick pattern (see above).
Return to Rose Cottage, HOUSE layer. Click Materials palette. Change current Pattern to brick pattern. Fill each chimney with the brick. De-select marquee.
Comment: Many pixel purest avoid all filters, and that could include 'noise'. But I happen to like the look you get with noise. Your choice to use or not use.
Optional: Break up the straight-line pattern of siding and brick by adding noise and removing some pixels.
Adjust > Add/Remove Noise > Add Noise
Check 'Uniform" and 'Monochrome" and enter 15% in dialog box.
Use Magic Wand to select a dark shade of gray in the siding, anywhere. Choose Selections > Modify > Select Similar. Check discontiguous and set tolerance to 15. OK.
Flood fill this selection with white. That should remove the rigid appearance of so many straight horizontal lines.
Deselect marquee.
The last step for the siding is to change the black outline to match, but we won't do that just yet. First let's finish the roof and blue trim.