What would be the pricing if I uploaded my own custom image to Linode
Uploading the image doesn't cost anything, it's the image itself that will cost you something. Linode's page on images states the price is $0.10 a month per GB. So, if you uploaded an image that was 5GB in size, you would be charged $0.50 a month. The provided link should give you more information on their limits and maximum image size.