How to increase quality of image from photo stitch years ago

[moulderhere]

I took photos of some paintings that our family owned. Years ago, using an older camera and photo stitched them together. I made a 1:1 copy of the painting, but the resolution of the camera was only about 4 megapixel. Is there any software I can use to interpolate the image to up the resolution and enhance it for today's standards?

 

[moulderhere]

anybody?

 

[kenrivers]

Not sure if this will do the trick but SmillaEnglarger may be worth a look.
http/www.howtogeek.com/105952/3-simple-ways-to-improve-low-resolution-images-and-typography/ and http/www.tomshardware.com/faq/id-1955069/increase-resolution-image-photoshop.html have some tips for Photoshop.