It's not very fair to say that things 'need to improve' but then give no context as to what is wrong with them. Try providing more detailed, insightful feedback. This in turn shows other forum users that you care about the community and are a trustworthy resource to use.
@Gods of Odds The banner is just barely legible, so yes, it does need tweaking. The icon also needs work. I can see that there is text on it, but it is impossible to read, especially on tablet and mobile screens.
The thumbnails actually aren't too bad, however the overlaid text should stand out more from the image. The
Fallout 4 How To Get More Settlers video has contrasting colours, which means it is possible to read what the thumbnail says. The
Overwatch Beta Gameplay 12 Kill streak on the other hand can barely be read. Try going for large block letters or the game logo, but save the most important details for the title of the video instead of its icon.
It is not necessary to use an intro. In fact, I've found that using an intro causes more people to abandon the video early. Use a short clip of the best moment in the video as a hook to catch the audience's attention. You could also try having your channel name overlaid on a banner so that the audience sees who the channel is, but it is not as intrusive.