[2.8] Option to globaly override previewed Texture in Texture shading

Currently in textured shading rendered texture is determined by selecting it in material node editor.

So during UV unwraping i have to set up materials and add uv grid just for UVing. There could be somewhere option to override that selected texture with preselected (UVgrid) or selectable texture.

For example in shading popup like that:

Also there could be some kind of texel density visualisation (eg. by color like in UV/image editor) But I don't know how it should be set up cause different objects could use different image resolutions.