You can create both SD and HD Texture Packs for Total Miner and have them included in the game.
Post #2 describes both the SD and HD formats, and includes a template file you can use to start making a texture pack.
Post #3 is a full list of all blocks and items to match against the template.
Here are the rules:
1. HD texture packs take quite a bit space on the game download file. For this reason we will be restricting our choices of community HD texture packs to only the very best submissions.
2. Your texture pack must be saved as a PNG file.
3. SD block and item textures are 16 x 16 pixels.
4. HD block textures are 64 x 64 pixels and Item textures are 32 x 32 pixels.
5. You must make every Block texture tileable. Search google to understand what this means and the techniques you can use to achieve it, but in a nutshell, if you lay down a bunch of the same texture side by side, there should be no visible seam.
6. All items must use fully transparent pixels for unused pixels.
7. Only Water, Lava and the Teleport Block textures support semi-transparency. All other Block textures must use fully opaque or fully transparent pixels.
8. The chart in post# 3 indicates which Blocks support (fully) transparent pixels. Read it carefully, most Blocks do not support transparency at all.
About using images from the internet:
Free use and Free commercial use are two very different things. If there is no free commercial licence attached to the image or website then that image cannot be used.
Legally, "copying an image" and "copying then modifying an image" are identical. Permission must be explicitly given.
I have any doubt in my mind that a texture has been copied from the internet and that texture does not have a Free Commercial Licence, then I will not select the texture pack. This is necessary because if someone filed a copyright infringement lawsuit, Microsoft will pull the game from the marketplace immediately.
**Any questions regarding the creation of TP's should be posted in this thread**
**TP submissions should be done here: [Link Forthcoming]**
Light MapThe Light Map is the first texture in the top left corner. It defines how light is coloured in Total Miner.
There are two types of light in Total Miner. Sun light and Block light. Block light is the light emitted from certain blocks, like torches, sun boxes, lava, gold, etc.
The Light Map controls the color and intensity of both types of light and any combination of each light.
By changing the color hues in the light map, you can define the color of the games atmospheric lighting.
Here is the default HD texture pack day and night light map:

The red border should not be in your light map. I've just put it here so the light map can be seen properly against the forums background. Your light map should be 64 x 64 pixels and have no border.
The light for sun light is defined on the x axis.
The light for block light is defined on the y axis.
Top Left is zero sun light and zero block light.
Bottom right is maximum sun light and maximum block light.
Top Right is maximum sun light, zero block light.
Bottom Left is maximum block light, zero sun light.
etc.
You are free to use this light map if you do not want to make your own.
Sky MapThe Sky map defines how the distant sea, horizon and sky look in game. The horizon is where the distant sea meets the distant sky.
Here is the default HD texture pack sky map:

You can see the image starts as a sky blue, then is a gradient down to a lighter blue, then goes dark again at the bottom.
The lighter area is the horizon (haze) and the darker area at the bottom is the sea. The first pixel defines the general sky color.
Sunset/Sunrise/Moonset/Moonrise MapsThese are special maps used to define the colours for the sun and moon when they are rising and setting.
The game picks two random points within each map and interpolates between those 2 points over the course of the rising/setting effect, giving the effect of color change.
Usually these would be gradients, but if you want random/crazy color variations, then you can do that too.
Example:

From left to right
1. Sunrise
2. Sunset
3. Moonrise
4. Moonset