Why are there so many different types of mileposts?
In 1845, legislation was passed resulting in the mandatory introduction of mileposts on our railways. The new posts were to be set at 1/4 mile intervals and measure the distance from a designated location along the route (usually a large station or junction).
Interestingly, the legislation didn't dictate the design of the posts, only that they should identify its location in-relation to a specified point on the route. Railway companies were free to use numbers or markers on their posts resulting in numerous designs being implemented, some companies opted to display full mileages including fractions, while others chose to display a mixture of mileposts and intermediate fraction posts instead, some signs even incorporated the location it was measured from for extra clarity.
As railways progressed, signs were painted yellow to be more visible in bad weather and the distances between them adapted to better suit local environments, this led to signs being placed at 1/8th of a mile intervals on some routes and as condensed as one chain (1/80th of a mile) on complex sections around the capital. In some locations, miles have been converted to kilometres, numbers substituted for lines or symbols and experiments with reflective materials have altered the appearance and meaning of many mileposts on the railway today.
With dozens of types, shapes and colours making up the portfolio of distance markers and mileposts used throughout railway history, most model manufacturers play it safe when portraying them, focusing on a simpler time when mileposts were small, white and displayed humble numbers and fractions, after all, that type can still be seen out there today. But if you really desire something a little less generic, why not study a prototype, bite the bullet and have a go at making one.